In a solid-state image sensor according to this invention, an image signal temperature variation suppressing unit changes a voltage value of a driver voltage applied to multiplying registers in response to variations in sensor temperature of a CCD image sensor. Thus, a charge multiplication gain of a charge multiplying unit is electrically controlled to suppress variations in signal strength of image signals due to the variations in the sensor temperature of the CCD image sensor. As a result, without relying on thermal control with which it is very difficult to realize high precision control, variations in the signal strength of the image signals due to the variations in the sensor temperature of the CCD image sensor are suppressed easily by controlling the charge multiplication gain of the charge multiplying unit based on the electric control, with which it is very easy to realize high precision control, performed by the image signal temperature variation suppressing unit in response to the variations in the sensor temperature of the CCD image sensor.