An indicator has an optical member including a protuberance formed on a front side and an indentation formed on a back side of the optical member in which the indentation is smaller than the protuberance in terms of a projection area and in which the front-side protuberance fits into the opening in a front face of the housing; and an LED light source disposed opposite the back-side indentation of the optical member. A center axis of the front-side protuberance and a center axis of the backs-side indentation are in line with an optical axis of the LED light source. Light originating from the LED light source passes through the back-side indentation and the front-side protuberance, exiting from the opening in the front face of the housing. Thereby, only the center of the rectangular opening looks lighting up brightly, rectangularly.