Abstract: Based on respective output signals (S4, S5, S7, S8) satellite sensors (4, 5) provided in an impact zone of a front section of a vehicle (1); an X-direction sensor (7) that detects an impact acceleration of the vehicle in a traveling direction thereof; a Y-direction sensor (8) that detects an impact acceleration in a direction that is orthogonal to the traveling direction, a control unit (6) that controls the operation of an air bag device (2) includes: a selection output portion that fetches, from among output signals (S40, S50) from the satellite sensors (4, 5) and an output signal (S80) from the Y-direction sensor (8), the output signal with the higher value; and a determination portion (9) that performs a collision determination of the vehicle (1) in response to the output signal (S7) from the X-direction sensor (7). A level of a threshold value used for the collision determination performed by the determination portion (9) is set based on the output signal selected by the selection output portion.