In a collision avoidance apparatus for a vehicle, a collision avoidance controller is configured to calculate a movement trajectory of a moving object moving on a road crossing a road that the vehicle is traveling on from a succession of locations of the moving object, calculate a movement trajectory of the vehicle using a speed of the vehicle, determine whether the movement trajectory of the moving object is a trajectory of a moving object likely colliding with the vehicle, and in response to determining that the movement trajectory of the moving object is a trajectory of a moving object likely colliding with the vehicle and that the moving object fails to be recognized by a camera due to a view of the moving object being obstructed, calculate a risk index for determining a collision avoidance measure and employ the collision avoidance measure in dependence upon the risk index.