PURPOSE: To permit to facilitate discrimination of a scope of spin overlap occurring at a time when turning by 360° or more and to enable detecting of an absolute angle, by a method wherein, in an angle detector, a cam, which slides over a fixed shaft following rotation, is mounted.

CONSTITUTION: A fixed shaft 2, fabricated with an outer peripheral thread, is secured to a case 1. Rotary discs 3 are rotatably attached to the fixed shaft 2 through bearings 4, and the discs 3 at both sides are coupled to each other with a coupling rod 5. A cam 6, screwing the fixed shaft, has a projection part 6a with a rotary angle of 90° at the outer periphery, and the coupling rod is inserted into a circle hole 6b. CCW switches 7 and 8 make contact with the projection part. If the rotary disc turns from -270° to +270°, the cam moves from A to G. In a scope AB covering -270°W-180°, the switch 7 actuates, and in a sphere covering +180°W+270°, the switch 8 works, which results in enabling to discriminate which overlap spin scope the cam is brought to.