An image decoding device is provided which performs expansion processing and reverse orthogonal conversion in fixed block units with respect to image compression data. The image decoding device is provided with an error block detection means (error block detection section 4) which receives a threshold value and an image signal in frequency bands, which determines whether or not an error is contained in block data based on the threshold value and the image signal in the frequency band and which outputs a detection state in the block data. <IMAGE>
