To enable a coding/decoding system to match a coded area with an assigned area and match an assignment area of a pre-stage system in matching with a coding area of a post-stage system.

An image signal into which an assigned area display information is inserted is fed to an input terminal 11. An assignment area display information detector 12 detects the assigned area display information from the image signal. The detected output is fed to a switch 13 as a control signal and fed to an adder 15 as coded area display information. The switch 13 is closed for a period of the assigned area denoted by the assigned area display information and open for the other periods. Thus, a coder 14 is used to apply compression coding to the image signal for the assigned area period only. The adder 15 inserts the detection output of the assignment area display information detector 12 to the compression coded output as coded area display information.