A vehicular collision detection apparatus includes a bumper reinforcement, a bumper cover, a chamber forming member, a pressure sensor, a pressure changing device, and a chamber state detecting device. The cover is displaceable relative to the reinforcement toward a rear of the vehicle upon collision. The chamber forming member is provided between the reinforcement and the cover and defines a chamber space that is deformable upon displacement of the cover. The pressure sensor senses pressure in the chamber space. The pressure changing device changes pressure. The chamber state detecting device detects whether or not the chamber forming member is broken based on the pressure, which is detected while the pressure changing device is in operation.