a first step of setting, as a reference temperature difference, a temperature difference between a void and a non-void in the concrete composite member covered with the steel plate in accordance with an on-site temperature and a concrete pouring temperature;

a second step of measuring the on-site temperature and the concrete pouring temperature before construction of the concrete composite member covered with the steel plate, and extracting a reference temperature difference corresponding to the on-site temperature and the concrete pouring temperature measured from the reference temperature difference set in the first step; and

a third step of measuring a steel plate surface temperature of an area in which concrete is poured using a thermal image during the construction of the concrete composite member covered with the steel plate, and determining, as a void, a section in which a temperature difference between the measured steel plate surface temperature and a temperature of a surrounding part thereof is equal to or greater than the reference temperature difference extracted in the second step,

wherein the on-site temperature in the first and second steps is set by a mean temperature of the steel plate surface temperature measured using the thermal image before pouring the concrete at a site or an outside air temperature at the site, and

wherein the reference temperature difference to be a value that increases or decreases whenever a difference between the on-site temperature and the concrete pouring temperature increases or decreases.