PURPOSE: To improve the efficiency of coding by extending an operation system clock period or reducing the number of bits for quantization.

CONSTITUTION: A system clock generation part 3 in a transmitting part 2 extracts a synchronizing circuit from an image signal inputted from a moving image source 1 and generates various timing signals. Plural A/D converters 1 to 4 (4 to 7) respectively execute A/D conversion based upon a sampling signal outputted from the generation part 3. Respective coders 1 to 4 (9 to 12) execute the coding of outputs from the A/ D converters 1 to 4 (4 to 7) based upon a prescribed conversion formula. Then modulators 1 to 4 (13 to 16) respectively modulate the outputs of the coders 1 to 4 (9 to 12) by means of respectively different modulation frequency bands and a multiplexer 17 synthesizes modulated outputs and outputs the synthesized signal to a coaxial cable 18. In a receiving part, demodulators respectively demodulate the modulated image signals and a D/A converter successively converts demodulated outputs into analog signals and outputs the analog signals to a monitor.