This invention provides a solar simulator measurement method capable of high-accuracy measurements with fast-response photovoltaic devices as well as with slow-response photovoltaic devices, and a solar simulator for implementing the method. A flash having a pulse waveform with a flattened peak is generated from a xenon lamp. The flash is sensed by an irradiance detector, its irradiance measured, and the irradiance of the light source is adjusted to fall within a prescribed narrow range based on the detected irradiance value. Then, the flash with irradiance within the prescribed range irradiates photovoltaic devices under measurement, and the current and the voltage output by the photovoltaic devices are measured at multiple points while a load of the photovoltaic devices is controlled. This process is repeated with multiple flashes to obtain an I-V curve for the photovoltaic devices.