Abstract: A compound infrared detector, having a thermopile detector which is constructed on one face of a pyroelectric insulating thin film and a pyroelectric detector which is constructed by installing electrodes on both faces of the insulating thin film in opposite relationship to an infrared ray responsive portion thereof.The compound infrared detector of the present invention can function both as a pyroelectric detector and as a thermopile detector. In addition, the pyroelectric detector and the thermopile detector can be installed on the identical focus of the identical optical system because they have a common infrared ray responsive portion and as a result thereof, the number of detectors and also the number of optical adjusting means and optical parts can be reduced relative to those used in the prior case when two detectors are used; that is, the mutual compensation effect of both kinds of detectors can be inexpensively attained.