A lightweight infrared sensor which is readily and stably erected to a substrate, the infrared sensor includes an insulating film; a first and second heat sensitive element are disposed on one surface of the insulating film separately; a first and second conductive film on one surface of the insulating film and are respectively connected to the first and the second heat sensitive element; an infrared reflection film on the other surface of the insulating film so as to face the second heat sensitive element; a reinforcing plate on which a sensor part window corresponding to a sensor part is formed and which is adhered to the insulating film; and a first and a second terminal electrode are respectively connected to the first and the second wiring film and formed on the edge of the insulating film.