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