To provide a vehicle collision detecting device for detecting a pressure change in a chamber arranged in a vehicle bumper, offering technology for discriminating the type of a colliding object with high accuracy.

The vehicle collision detecting device comprises a chamber member 7 arranged in the vehicle bumper 1, a pressure sensor 9 for detecting pressure in a chamber space 7a, a vehicle speed sensor 11, and a controller 13. The controller 13 uses an approximate expression or a table showing a correlation between a maximum value for the pressure change detected by the pressure sensor 9 and the absorbing energy of the vehicle bumper for finding the absorbing energy of the vehicle bumper 1, uses an expression: M=2E1/V2 for calculating an effective mass M of the colliding object from the absorbing energy E1, and discriminates the type of the colliding object to be a pedestrian when the effective mass M is a threshold value or greater or within its range.