A compression encoder uses an arbitrary normalization coefficient and a preset table to achieve a compression of image signal with a desired compression rate. Since the normalization coefficient and the table data are sent to an image signal decoding and reproducing apparatus together with the compressed image data, the reproducing apparatus can restore the original image from those data items. Furthermore, in the encoder, when an amplitude value of the data exceeds a predetermined value, an overflow sensor means the condition so as to produce normalized data in addition to the Huffman-encoded data. The reproducing apparatus achieves the image signal decoding and reproducing operations by use of the normalized data and the Huffman-encoded data. With these apparatuses, the picture quality can be prevented from being lowered due to an overflow in the encoding operation.