Disclosed is a vehicle-state detecting device which comprises acceleration sensors (1, 2, 3) each provided for an axis such that acceleration in directions along the three axes can be detected; and a computing unit (7) that calculates the direction of gravity from the vector sum of results detected by the acceleration sensors provided for the respective axes, corrects the inclination of the vehicle-state detecting device with respect to the vehicle to which the vehicle-state detecting device is attached, and detects acceleration in the longitudinal direction, the lateral direction, and the vertical direction of the vehicle.