The signal processing circuit of the present invention comprises a drive unit and a processing unit for picture signal. The drive unit supplies each of the shift pulses separately to the electronic shutter shift register and the readout shift register. The processing unit for picture signal designates a control start position of a digital picture signal outputted from an A/D converter and performs interpolation processing thereon along the horizontal direction and the vertical direction. The drive unit adjusts cycles of each of the shift pulses for controlling a vertical-line readout rate of the solid-state imaging device, and then intermittently reads out the analog picture signal from the solid-state imaging device. The processing unit for picture signal performs vertical-line interpolation processing in accordance with the vertical-line readout rate for extending a part of picture area of the digital picture signal.