To detect a thermal image having movements via a simple structure.

This sensor uses a pyro-electric infrared ray detector array 1 to identify an event in a scene 12. Then the sensor including the array 1 is directly attached to a read integrated circuit 2 so as to make each element touch electrically one of input terminals set to the circuit 2. The array 1 out on the circuit 2 is positioned at the focus of an infrared ray transmitting lens 11, so that an image of the scene 12 is formed on the array 1. Then the circuit 2 and the array 1 are contained in a package 18 that is connected to a microprocessor 20 via a circuit board 19. Both microprocessor 20 and circuit 2 coact to detect the occurrence and position of the event included in the scene 12.