A collision detection apparatus includes: an energy absorption member that possesses conductivity and absorbs impact energy by being crushed in a front-rear direction; two contact members that possess conductivity and are respectively disposed in contact with front and rear end surfaces of the energy absorption member in order to press and crush the energy absorption member in the front-rear direction; a electric resistance detector that is electrically connected to both of the two contact members in order to detect variation in an electric resistance value accompanying crushing of the energy absorption member; and a displacement calculator that calculates a displacement amount of the energy absorption member in the front-rear direction on the basis of the variation in the electric resistance value detected by the electric resistance detector.