PURPOSE: To improve microphone stability by using a pyroelectric ceramic material based on lead titanate indicated by a specified formula in a pyroelectric detector element.

CONSTITUTION: PbO, TiO2, Mn2O3 and La and the oxide of one or more rare earth metals such as Sm and/or Gd or the like are mixed by prescribed weight and the mixture is calcined, then finely pulverized, worked and molded. It is sintered and this pyroelectric ceramic material based on the lead titanate indicated by the formula (RE is the rare earth metal 0.04≤x≤2.0) is obtained. Then, NiCr electrodes 3 and 4 are arranged on both sides of the pyroelectric detection element 1 using the material and fixed to a substrate 7 by two supporting members 10 and 11. The electrode 4 is electrically connected through a connection wire 5. Further, an electronic circuit provided with a field effect transistor 13, and diodes 14 and 15 housed in an outer jacket 12 is provided, enclosure is performed by the outer jacket provided with a window for transmitting a wavelength range sensitive to radiation and a pyroelectric detector is formed.