PURPOSE: To improve SN ratio of an MOS type solid-state image pickup device by providing a clamping circuit to a potential fixing circuit having a horizontal switching circuit that connects a vertical signal line and a horizontal signal line through a coupling condenser to which signal voltage is applied.

CONSTITUTION: A vertical signal line 12 and a horizontal signal line 11 are connected by a horizontal switching circuit 9. Signal charge of the signal line 12 is transferred imperfectly to the first condenser 9C through the first transfer gate 9B in horizontal blanking period, and further transferred imperfectly to a storage condenser 9E. Signal charge of the condenser 9E is transferred to the signal line 11 by the horizontal scanning pulse of a horizontal scanning circuit 10. An amplifier 4A is connected to a clamping circuit 6 through a coupling condenser 5 and outputted through an amplifier 4B. In such a way, SN ratio of the MOS type solid-state image pickup device is improved.