To provide a cable holding method for a control unit which is capable of surely keeping a flat cable slack and insulated from parts and easily connecting the flat cable.

The cable holding method is provided for the control unit which is equipped with the flat cable 5 composed of electric wires arranged on the same plane and a plurality of boards 1, 2 mounted with circuit parts. The folded part of the flat cable 5 is folded into a Z shape by forming, and is inserted into a cable holder 6 for slacking the flat cable 5, wherein the cable holder 6 is provided in parallel and by a connector 4 which connects the flat cable 5 of the board 2.