An image sensor includes: a readout circuit that reads out a signal to a signal line, the signal being generated by an electric charge resulting from a photoelectric conversion; a holding circuit that holds a voltage based on an electric current from a power supply circuit; and an electric current source including a transistor having a drain part connected to the signal line and a gate part connected to the holding circuit and the drain part, the electric current source supplying the signal line with an electric current generated by the voltage held in the holding circuit.