An imaging device includes a sensor that is color coded by using high-sensitivity pixels having higher sensitivity to incident light than chromatic color pixels and an automatic exposure function that allows the imaging device to control exposure according to illuminance in an imaging environment. An algorithm in the automatic exposure function that determines a reference color in a level diagram according to the illuminance uses the high-sensitivity pixels as the reference color in a low illuminance region where the gain of the sensor is set to a maximum, while using green pixels, which are the chromatic color pixels, as the reference color in a standard illuminance region where the gain of the sensor is set to a minimum.