A lightweight infrared sensor that detects a temperature at a portion spaced apart from a circuit substrate with high accuracy, is installed on the circuit substrate easily and stably, and includes an insulating film; a first and a second heat sensitive elements are disposed on one surface of the insulating film separately; a first conductive film on the insulating film that is connected to the first heat sensitive element; a second conductive film connected to 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 plurality of terminal electrodes formed on one end of the insulating film and fitted into an external connector; an edge reinforcing plate adhered to one end of one surface of the insulating film; and a mounting hole that is formed on the other end.