To provide a crew detecting system which not only can accurately detect the seating conditions of passengers, but also can appropriately control an air-bag device, etc., based on the detected results.

A crew detecting system is constituted in such a way that an antenna electrode is arranged on a seat and/or the periphery of the seat and an electric field is generated in the periphery of the antenna electrode. Then the system detects the information on the current flowing to the antenna electrode base on the electric field, discriminates the seating conditions of passengers on the seats based on the information, and sets the air bag of an air bag device to a prescribed operation mode based on the information. The antenna electrode 4 has at least antenna electrode sections 4a-4d formed of conductive members and a space section G where no conductive member exist is formed inside the outer peripheral edge of each electrode section 4a-4d.