An image sensor includes a pixel and a control circuit to detect the optical signal transmitted by a signal line. The pixel includes a photodetector, an amplifier circuit configured to amplify an optical signal from the photodetector, and a first switch configured to control whether to output the optical signal from the pixel to the signal line. The control circuit includes a first capacitor connected with the signal line and an integrator connected with the signal line via the first capacitor. The control circuit is configured to successively supply a first potential and a second potential different from each other to the signal line in a state where the first switch is non-conductive, and measure an amplification rate determined by the first capacitor and the integrator based on outputs of the integrator when the first potential is supplied and the second potential is supplied.