A solid state image pickup device which includes a pixel unit having a plurality of pixels arranged in a two-dimensional matrix shape and having a mechanism for converting an optical signal into an electrical signal and outputting the resultant signal, a column processing circuit for performing column processing of the signal from the pixel unit, a calculating circuit for calculating a processing result of the column processing circuit, a frame memory unit, an internal interface for connecting the calculating circuit and the frame memory unit, an external interface for connecting an external unit or device and the frame memory unit, and a connection switching circuit for switching a connection of the frame memory unit relative to the internal interface and the external interface.