To provide a traveling propriety determining device for determining whether a mobile body can pass, even when there is an obstacle.

The device comprises an imaging means 101 for photographing the circumference of the mobile body; a first determining means 103 for determining whether an object exists in a first image area; a distance measuring means 104 for measuring the distance from the imaging means to the object; a first calculating means 103 for calculating a first determination value, based on the measured distance and the distance between the imaging means and the object on an image; a determining means 106 for determining whether the mobile body can pass, based on the first determination value; a second determining means 105 for determining whether a projected object from the mobile body exists in the second image area; a second calculating means 105 for calculating a second determination value, based on the distance to be measured from the imaging means to the projected object and the distance between the imaging means and the projected object on the image; and an alarm means 107 for issuing an alarm, when the mobile body cannot pass after determining the passage of the mobile body, based on the second and first determination values.