a first mirror having a first reflecting surface extending in a first direction and a second direction perpendicular to the first direction and being partially light transmissive, the first mirror comprising a multilayer reflective film;

a second mirror having a second reflecting surface facing the first reflecting surface and being partially light transmissive;

an optical waveguide layer that is located in part of a region between the first mirror and the second mirror and propagates light in the first direction by being reflected by the first mirror and the second mirror multiple times; and

an optical element that is disposed on the first mirror on a side opposite to the first reflecting surface and emits incident light from the optical waveguide layer, which passes through the first mirror, in a direction different from an incident direction by refraction and/or diffraction,

wherein the optical element emits (1) the incident light entering in a direction such that a first direction component of the emitted incident light is smaller than a first direction component of an incident direction of the incident light, by refraction and/or diffraction or (2) incident outside light entering from the outside of the optical device in a direction such that a first direction component the entering incident outside light is larger than a first direction component of an incident direction of the incident outside light, by refraction and/or diffraction, and

wherein a direction of light emitted from the optical waveguide layer, which passes through the first mirror and the optical element, or an incident direction of light introduced into the optical waveguide layer, which passes through the optical element and the first mirror, is adjustable.