To assign a code bit to an important part with emphasis by reducing assignment of code bits to non-important parts in advance without revising a coder.

The image processing unit consists of an importance designation means 10 that designates importance of a received image frame, a low pass filter control means 12 that validates a low pass filter according to the designation of the importance designation means and a low pass filter 13 that eliminates high frequency components of the received image frame. The image processing unit generates moving image data by eliminating the high frequency components of the received image without deteriorating the image quality of the image frame with high importance, thereby suppressing the amount of code generated in the case of orthogonal transform coding in the coder.