A rotation angle measurement device includes: relative angle detection means 12 including a reference support 26 whose rotation is regulated in a fixed range in an arbitrary direction of a rotation axis, and a driving rotating body 22 which is coupled to the reference support 26 and is axially supported so as to be all-round rotatable with respect to the reference support 26, the relative angle detection means 12 which detects a relative rotation angle of the rotating body 22 with respect to the reference support 26; and non-contact angle detection means 40 which detects a rotation angle of the reference support 26 with reference to a position that does not contact with the rotating body 22 and the reference support 26. This provides improved accuracy in indexing the rotation angle of a rotating moving shaft and easy installation onto the rotating moving shaft.