A simulated sunlight irradiation apparatus (100) has transmittance adjustment members (13a and 13b) provided above an irradiation surface of a light guide plate (10) and in the vicinity of either incident face of the light guide plate (10) on which simulated sunlight is incident. The transmittance adjustment members (13a and 13b) adjust the transmittance of light in a portion of a wavelength band of simulated sunlight that is emitted from the irradiation surface of the light guide plate (10), thus bringing about improvement in spectral coincidence of the simulated sunlight. This provides a simulated sunlight irradiation apparatus that can radiate simulated sunlight with high spectral coincidence.