To obtain a passive-type infrared detection apparatus by which a moving object can be detected by a method wherein, when output signals of respective infrared detection elements are in a saturated state, peak values of the signals are found on the basis of the inclination, the saturation time of the rise and the fall of their waveforms and their difference or their ratio is compared with a definite value.

An infrared detection element 2 is provided with infrared detection elements 2a, 2b whose detection area can be set so as to be different from each other, and whether output signals of the elements 2a, 2b are in a saturated state or not is discriminated by a saturation discrimination means 3. When the saturation state is discriminated, peak values of the signals are found by a peak-value computing means 4 on the basis of the inclination of a rise and the inclination of a fall up to the saturation state of their waveforms from the output signals, on the basis of the continuation time of the saturation state and on the basis of a saturation level, and the peak values are output to a computing means 5. The means 5 finds the difference between the respective peak values or their ratio, and a discrimination means 6 outputs a detection signal when the values are at a detection level or higher. In this manner, even when the output signals of the elements 2a, 2b are in a saturated state, a human body can be detected surely when the peak values are measured in advance.