An object of this invention is to realize both stable clamping operation of a CDS circuit and an operation of draining unnecessary charges from a CCD. To achieve this object, during the storage period of an image sensing element, (A) vertical CCDs perform high-speed transfer or all the vertical CCDs are fixed to a LOW voltage, (B) a horizontal CCD is stopped, (C) the reset pulse of a floating diffusion amplifier is not stopped, and (D) a clamping pulse supplied to the CDS circuit is kept output. During this operation, the reference level of the floating diffusion amplifier is clamped. Stable clamping operation can, therefore, be executed during the storage period.