A perovskite type manganese oxide thin film capable of working at temperatures within an electron cooling range and a high sensitivity infrared sensing element using the same thin film are disclosed. The thin film of perovskite type manganese oxide containing an element Ca or Sr and elements La, Mn and O is characterized in that a metal-insulation phase transition point of the thin film lies within a range of temperatures obtainable by a thermoelectric cooling method. The perovskite type manganese oxide is a thin film produced by a sol-gel method and the film is used for manufacturing an infrared sensing element.