To reduce the degradation of information even at the time of a high compression rate to easily perform expansion of a reduction picture and data emphasis in a small scale at a high speed.

A part of picture data as the compression object is blocked into an optimum quantity of data by a blocking processing part 12, and data is converted into a coefficient string by frequency conversion processing and quantization processing 13 using wavelet conversion. Thereafter, encoding processing 14 is performed by the encoding method set to each coefficient string area to generate compressed data 15 constituted by bands. Decoding processing 16 is performed for compressed data, and the coefficient string is converted into data by frequency inverse conversion processing and inverse quantization 17. High frequency band coefficient processing 18 is performed where coefficients of high frequency bands are processed at need to emphasize the edges of a picture, and a restored picture is generated by block reconstitution processing 18 which integrates data. Only several low frequency bands are expanded to generate a reduction picture.