A sunlight simulator and solar cell measuring device consisting of detecting device is disclosed, in which the housing is a closed space consisting of an opening gate, the closed space is internally installed with a light source which is used to emit a light toward the opening gate, and a splitting unit is installed on the travelling path of the light for dividing the light into a first light-beam and a second light-beam, herein the first light-beam is projected onto the solar cell under measurement located at the opening gate as a solar cell measuring device; in addition, a detecting device is installed on the travelling path of the second light-beam for receiving the second light-beam, and then a signal can be outputted by the detecting device in order to monitor the irradiation variation of the light emitted by the light source, thus ensuring the precision of the solar cell measurement.