Abstract: External noise in an infrared sensor for a ceiling type human detector is suppressed by increasing the conductivity between a conductive window and the can and improving the temperature compensation by offsetting any difference in the electromotive force per unit area of the inside and/or outside electrode of the sensitive element consisting of coaxial electrodes with different areas. In a pair of electrodes for ceiling mounting the electromotive force is larger than in a pair of lower electrodes for floor mounting. The sensor improves a total sensitivity for use in the infrared sensor for a wall installation type human detector, on account of improving performance and reliability of the pyroelectric infrared sensor for use as a human detector.