The present invention includes a driving behavior detecting unit (3) mounted on an automotive vehicle (A) and having at least an accelerator sensor (2) and is operable to detect the driving behavior on the basis of the acceleration of the automotive vehicle A detected by the acceleration sensor (2), in which a setting cant state detecting unit (11) automatically detects, on the basis of the frequency of occurrence of the acceleration at a plurality of angles of inclination on a plane containing a predetermined axis of the automotive vehicle (A) and a predetermined axis of the driving behavior detecting unit (3) installed so as to incline relative to this predetermined axis, at least the angle of inclination of an anteroposterior axis of the driving behavior detecting unit (3) installed relative to the anteroposterior axis of the automotive vehicle (A) is automatically detected.