An object position detection apparatus 1 includes a distance image generation unit 10 which generates a two-dimensional distance image by measuring a distance to a subject including an object on the basis of a light transmission time, an object image generation unit 16 which generates an object image in which the object is extracted from the distance image of the subject, and an installation angle detection unit 20 which detects an installation angle of the distance image generation unit 10. The object image generation unit 16 includes a differentiator 17 which performs a process of removing a background other than the object from the distance image of the subject and a threshold value d for removing the background in the differentiator 17 is set in response to the installation angle of the distance image generation unit 10 detected by the installation angle detection unit 20.