To provide a designing method of the number of turns of a flat cable of a feeding device to a moving body, by which setting of the number of spiral turns of a flat cable can be easily performed when the size of a of equipment and a necessary delivery length are given.

The number of spiral turns of a flat cable 3 on a core 2 is set to at least the number of turns represented by formula, L0/[2π(R1-R0)] wherein, RO is a minimum winding radius of the flat cable 3 spirally wound on an outer periphery of the core 2 when it is drawn-out to the maximum, and R1 is a maximum winding radius of the flat cable, and L0 is a necessary draw-out length from a winding diameter contact 12 upon draw-out of the flat cable 3 from the outer periphery of the core 2 in a tangential direction.