To provide an image signal processor capable of interpolating a high frequency subband component.

This image signal processor for interpolating a wavelet- transformed data error is provided with a means that selects whether or not the error data of high frequency subband component coefficient data are to be interpolated in accordance with the error detection results of the subband component coefficient data by an error detecting device. The image signal processor for interpolating the wavelet-transformed data error is provided with a means for comparing a frame with the preceding and subsequent frames in low frequency subband coefficient data.