A jack (10) of the invention includes a holding body (9) having an insertion hole (15) into which an optical plug is able to be inserted, a window material (6) through which infrared radiation passing through the insertion hole (15) is transmitted, and a light reception unit (2) which detects infrared radiation of 6 μm or more and 15 μm or less transmitted through the window material (6). The window material (6) is provided in the holding body (9) so as to prevent water from intruding into the light reception unit (2), and arranged at a bottom of the insertion hole (15). Thereby, it is possible to give a waterproof property to an element which receives infrared radiation without limitation to design or aesthetic appearance of an electronic apparatus.