A computer of a collision possibility determination device has a pixel position setting section, a travel vector calculating section, a vector direction determining section, and a collision possibility determining section. The pixel position setting section sets a travel direction pixel position in an image of view ahead of a vehicle and a circle with a specific radius from the set travel direction pixel position. The travel vector calculating section calculates a travel vector of an object that exists in the travel direction of the vehicle. The vector direction determining section determines whether an orientation of the travel vector matches a direction toward the inside of the circle. The collision possibility determining section determines a possible collision between the vehicle and the object when the orientation of the travel vector matches the direction toward the inside of the circle.