To provide an encoder reduced in computation processing load and improved in coding efficiency.

The encoder adaptively divides each block constituting a frame in a motion picture signal inputted from an imaging apparatus into sub-blocks for encoding. The encoder comprises: a new image pick-up region specifying means for specifying a region in a frame different from a previous frame using operation information for the imaging apparatus as the input; and a block dividing means for dividing each block constituting the frame into sub-blocks on the basis of the result specified by the new image pick-up region specifying means.