the resin-based material comprising at least one composite material comprising a resin matrix and inorganic particles dispersed in the resin matrix,

the inorganic particles comprising:

at least one group of identical diameter spherical particles (G-PID) comprising spherical inorganic particles with a specific average primary particle diameter in a range of 100 nm to 1,000 nm and having a number-size distribution in which 90% or more of all particles have particle diameters falling within a range of the average primary particle diameter-5% of the average primary particle diameter to the average primary particle diameter+5% of the average primary particle diameter; and

a group of superfine particles (G-SFP) comprising inorganic particles with an average primary particle diameter of less than 100 nm,

the at least one group including one or more groups of identical diameter spherical particles, wherein

the one or more groups of identical diameter spherical particles are A groups each represented by G-PID_m, wherein A is the number of the groups, m is 1 where A is 1 or m is a positive integer of 1 to A where A is 2 or more, and the average primary particle diameter of the group increases with increasing m,

the groups represented by G-PID_m have average primary particle diameters differing by 25 nm or more from each other,

the group of superfine particles has an average primary particle diameter 25 nm or more smaller than that of the group represented by G-PID₁,

the at least one composite material satisfies the relation n_(Mx)<n_(G-PIDm), wherein n_(Mx) is a refractive index of the resin matrix for light with a wavelength of 589 nm at 25° C., n_(G-PIDm) is a refractive index of the spherical inorganic particles of each group represented by G-PID_m for light with a wavelength of 589 nm at 25° C., and the relation is satisfied for each n_(G-PIDm), and

the at least one composite material has a short-range order structure in which the spherical inorganic particles of all the groups of identical diameter spherical particles in the resin matrix have an arrangement structure satisfying:

Condition 1 where a radial distribution function graph plotted with r/r₀ on an x axis and a radial distribution function g(r) on a y axis and showing a relationship between r/r₀ and the g(r) for r, wherein r/r₀ is a normalized dimensionless number calculated by dividing a distance r from a center of any spherical inorganic particle in the composite material by an average particle diameter r₀ of all spherical inorganic particles dispersed in the composite material and the g(r) represents a probability of existence of any other spherical inorganic particle at a point apart by the distance r from the center of the any spherical inorganic particle, has peaks among which a peak closest to an origin provides a distance r₁ between nearest neighbor particles as the r value corresponding to a top of the peak, and the distance r₁ between nearest neighbor particles is 1 to 2 times the average particle diameter r₀ of all spherical inorganic particles dispersed in the composite material; and

Condition 2 where the radial distribution function graph has peaks among which a peak second closest to the origin provides a distance r₂ between second nearest neighbor particles as the r value corresponding to a top of the peak, and the radial distribution function g(r) has a local minimum value of 0.56 to 1.10 between the distance r₁ between nearest neighbor particles and the distance r₂ between second nearest neighbor particles.