A quantizer quantizes a “prediction error” as a difference value between a pixel X to be compressed and a prediction value X′. A variable-length encoder inputs a quantization number obtained from a quantization table of the quantizer, and outputs a variable-length code (compressed code). A prediction value candidate calculation module calculates candidates 1 through k for a prediction value on the basis of peripheral pixels A, C, and B, and transmits them to a multiplexer (MPX). A prediction value determination module determines a prediction value among the candidates 1 through k for a prediction value on the basis of an intermediate value correspondence table and an intermediate value—image format correspondence table depending on an image format, and transmits a control signal to the multiplexer (MPX). The multiplexer (MPX) outputs one of the candidates 1 through k for a prediction value as a prediction value X′.