A method for inserting information in a compressed image is provided to re-detect inserted data easily without bad influence in picture quality although the information is inserted into a compressed image signal. A method for inserting information in a compressed image including a step for measuring sum total of a AC coefficient within a quantized discrete cosine transformation block and a step for changing the sum of the AC coefficient in the block into an odd number or an even number according to a value of a bit of image information. The DCT block includes a pixel of 8x8. A DC coefficient represents average of the coefficient in the block.
