To provide a detection processing device of a vehicle occupant protection system, facilitating a proper treatment such as part replacement of a control circuit by outputting an alarm according to the kind of a reset factor.

A development current is output to an airbag device 15 in response to development determination of a development determining part 6 provided in a control circuit 5 including a microcomputer or the like. A memory part 9 is connected to a CPU 8 that is a central arithmetic processing unit of the control circuit 5. In the memory part 9, a region in a RAM part 9b, where signal data including a forced reset signal can be read and written, is divided into a general RAM part 10 and a WDT circuit diagnosing RAM part 11. To the control circuit 5, an external WDT circuit 17 comprising ASIC is connected in addition to an internal WDT circuit 12, and runaway or the like is detected to distinguish the restart factor.