Abstract: A solar simulator for measuring the current-voltage characteristics of photovoltaic devices, in which an irradiated test plane of the object to be measured is disposed opposite an illuminating surface of the light source, the whole test plane of the photovoltaic devices is divided imaginarily into a plurality of sections, and a selected member for adjusting irradiance is disposed opposite the test plane of each imaginary sections so as to equalize or substantially to equalize the irradiance by the light source at every irradiated test plane of the sections, after which light from the light source is directed onto the test plane of the object to be measured.