An image encoding and transmitting system is an image transmission system for transmitting digital data such as TV telephones. The system for dividing input frame data into a plurality of blocks before transmitting them comprises on its sending side an intra-frame/inter-frame determiner for receiving intra-frame data and inter-frame data and selecting either of them for output, and a difference collator for having the intra-frame/inter-frame determiner compulsorily output intra-frame data at the time of data input for the next frame when one or more data in each block forming inter-frame data are larger than a predetermined threshold. The system also comprises on its receiving side an picture element domain frame data storage for storing received data in the picture element domain, and a motion vector detector for detecting according to the contents in the storage a motion vector using the data in the block surrounding the discarded block in order to guess the data in the discarded block.