An irradiation apparatus includes a light source unit to emit light, a light condenser, disposed on a light path of the light emitted from the light source unit, to condense the light emitted from the light source unit, a first diffuser, disposed on a light path of the light exiting from the light condenser, to diffuse the light condensed by the light condenser, an optical equalizer, disposed downstream of the first diffuser, to equalize a luminance distribution of the light entering the optical equalizer from the first diffuser and to output the light having the equalized luminance distribution, and a second diffuser, disposed downstream of the optical equalizer, to diffuse the light exiting from the optical equalizer.