PURPOSE: To enhance safety by simple constitution such that an incident ultrasonic wave is reflected three times by the inner surface of an ultrasonic reflecting plate and totally reflected always in parallel to the incident wave in the exact opposite direction.

CONSTITUTION: In an automatic propelling unmanned feed vehicle 1, a reflection type ultrasonic body detection apparatus 3 is constituted by using a transmitting- receiving ultrasonic element or arranging a transmitting ultrasonic element and a receiving ultrasonic element in close vicinity to each other and an ultrasonic reflecting body 4 formed by mutually arranging three plates at a right angle is provided to a vehicle body. Therefore, the ultrasonic wave incident on the reflecting plate 4 is reflected three times by the inner surface thereof and totally reflected as it is as a reflected wave 6 always in parallel to an emitted wave 5 in the exact opposite direction. Even when the vehicle 1 largely inclines with respect to the preceding vehicle 2 during the running on a circumference-of-circle passage, the reflected wave 6 returns to the apparatus 3 within a range of ±45° being the reflection directing angle of the reflecting plate 4 and can be detected.