A movable plate provided with movable contact points rotatable around a shaft hole of a base plate is disposed and a plurality of stationary contact points are on the base plate in both side of the shaft hole in such a way to surround the shaft hole with the stationary contact points. The stationary contact points are connected or disconnected to the movable points of the movable plate depending on rotation of the movable plate. Location of the stationary contact points at a wide angular range enables the row number of circular arcs having the stationary contact points to be reduced, and the distance from the shaft hole to the circular arc Ce of the outermost peripheral stationary contact point is not large, thus downsizing the whole size. As a result, the material expenses of the stationary contact points are reduced.