The position of the moving section in a robot is accurately and easily adjusted to a position of the origin by: setting a moving section being rotatably secured to a reference section through a rotary shaft in a manner that the axis of the rotary shaft is disposed horizontally; mounting an angular sensor for detecting an inclination angle of the moving section with respect to the origin, such as a level, on the moving section at a predetermined position thereof with respect to the axis of the rotary shaft; and rotating the moving section about the rotary shaft in response to a detected inclination angle. The apparatus therefor includes the angular sensor, such as a level, disposed on a mounting member and held in a position by a positioning member, and a rotating member for rotating the moving section about the rotary shaft in response to a detected inclination angle.