To obtain high sensitivity, by forming a surface electrode and a back electrode on the whole front and back surfaces of a pyroelectric element, and by dividing the pyroelectric element after polarization to form plural independent pyroelectric elements, and by loading the divided pyroelectric elements directly on a base plate.

Through holes 7c are formed on a base plate 7 on which pyroelectric elements 6a, 6b having electrodes formed on the whole front and back surfaces thereof are loaded, and the through holes 7c reduce a contact area between the pyroelectric elements 6a, 6b and the base plate 7. The pyroelectric elements 6a, 6b are loaded in accordance with loading positions of the pyroelectric elements 6a, 6b on the base plate 7, and a back electrode is stuck conductively relative to a pattern on the base plate 7 by a conductive adhesive. A resist layer prevents conduction between a surface electrode of the pyroelectric elements 6a, 6b and the back electrode by a conductive paste 9. The pyroelectric elements 6a, 6b are independent having electrodes on the whole surfaces, and are not formed by installing plural electrodes on the same element, therefore, heat is conducted to a part where the electrodes of the pyroelectric elements 6a, 6b are not formed, to prevent a temperature rise of an adjacent electrode.