A moving picture decoding method and a decoder for restoring a moving picture signal is disclosed. The decoder includes a decoding unit that decodes the differential signal, a motion vector, and a shape information indicating a shape of a block that becomes a unit for the motion compensated prediction by using an encoded bitstream. The shape information indicates an accuracy of virtual pixel and an interpolation filtering method. The decoder also includes a motion compensating unit that determines that the accuracy of virtual pixel and the interpolation filtering method is to be used in generating the predicted picture based on the shape of the block that becomes the unit for the motion compensated prediction, and generating the predicted picture containing the virtual pixel with reference to the reference pictures stored in a frame memory using the motion vector decoded by the decoding unit according to a determination result.