PURPOSE: To enable high-efficiency encoding without complicating circuit configuration by performing a prescribed processing to information signals and transmitting a first code word and a second code word.

CONSTITUTION: Input image information aa is supplied to a block dividing means 1 and the output signal is supplied to a DCT transformer 2 to perform two-dimensional DCT at every block. As the result of two-dimensional DCT, a transformation coefficient F(U, V) is derived. Further, a quantizing means 3 quantizes the transformation coefficient according to a prescribed method. This quantized transformation coefficient is encoded by using a '0' pattern detecting means 4 and a variable length encoding means. At the means 4, the nonsignificant coefficient of a requantized transformation coefficient corresponding to a previously prepared pattern is encoded. At the means 5, remaining transformation coefficients excluding the non-significant coefficient previously stored in the means 4 from requantized arrangement are encoded.