To provide a variable resistor whose resistance value can be changed stably and repeatedly within a specified range according to its operation.

A resistance layer 33 of a variable resistor is provided with a projection part 33a on the outer circumference of one end and a projection part 33b on the inner circumference of the other end. The respective tip ends of the projections 33a and 33b is on the positions P11 and P12 and they have an overlapping width D in a radial direction. When a sliding element of the variable resistor is turned counterclockwise and the sliding part moving as indicated by a dotted line A is on the position P11, the projection parts 33a and 33b are overlapped with each other in the overlapping width area, so that the sliding part moving as indicated by a dotted line B is slid at the projection part 33b. When the sliding part exceeds the position P12 at the end part of the projection part 33a and becomes in non-contact therewith, only the sliding part is slided in the projection part 33a. The sliding part does not become in non-contact with the layer 33 at the same time and the resistance value does not become infinite. In addition, the resistance value can be changed repeatedly within a specified range according to operation.