A temperature distribution measurement apparatus has an infrared array sensor that includes a pyroelectric substrate with infrared array receiving electrodes and electrodes for compensation formed on its front side and opposing electrodes formed on its backside. Also included is an infrared lens to focus incident infrared lights on the array sensor, a chopper to cut off the incident infrared rays intermittently and a rotating part carrying and rotating parts of the apparatus. The detector elements of the infrared array sensor are laid out vertically and parallel with one another. A horizontal temperature distribution is measured by a lateral scanning with the rotating part rotating horizontally while a vertical temperature distribution is measured by driving the chopper in front of the infrared sensor. Thus, a two dimensional temperature distribution of an empty space is measured. The number and the position of persons in the empty space attained from the temperature distribution measurement data is useful for controlling air conditioners.