A positional measurement system includes an electromagnetic wave source which emits an electromagnetic wave, a lens system which has a first lens surface, an electromagnetic wave shield section provided around a center axis of the first lens surface, and a second lens surface, and causes the electromagnetic wave having entered by way of the first lens surface exclusive of the electromagnetic wave shield section to exit from the second lens surface, to form an electromagnetic wave concentrated area at a position opposite the electromagnetic wave source, a receiving device which detects the electromagnetic wave concentrated area formed by the lens system, and a computing device which measures a position of the electromagnetic wave source based on information detected by the receiving device on the electromagnetic wave concentrated area.