An image pickup system includes an optical sensor configured to pick up an optical image of an object illuminated with light of a plurality of colors emitted from a plurality of semiconductor light emitting elements with an image pickup device and detect each of light amounts of the light emitted from the plurality of semiconductor light emitting elements, and a controller including hardware. The controller adjusts color balance based on the light amounts of the plurality of colors detected at the optical sensor and sets an exposure timing of a light amount detecting unit according to image pickup operation of the image pickup device.