A collision probability calculation apparatus capable of accurately calculating a collision probability that one's own vehicle will collide with an object around the own vehicle (referred to as a nearby object). In the apparatus, a position of the nearby object and a traveling speed and a traveling direction of the own vehicle are acquired. A collision probability map is generated on the basis of the traveling speed and traveling direction of the own vehicle. A width of a traveling lane of the own vehicle is acquired and the map is corrected in response to the width of the traveling lane. Thereafter, a collision probability associated with the position of the nearby object is corrected in response to the position of the nearby object. The corrected collision probability is outputted as a more accurate collision probability that the own vehicle will collide with the nearby object.