To provide a vehicle interference prevention device capable of safely predicting the position of a vehicle concerned even the frequency of communication using radio waves is less by finding out the existence range of the vehicle while considering time required for the measurement of the vehicle position and capable of avoiding the interference of an unmanned vehicle or a manned vehicle.

An unmanned vehicle 10 finds out a circle 70 defining a distance obtained when a manned vehicle 11 finally acquired (received) by an inter-vehicle communication device moves from a position P (position at a certain point of time) based on the positional data of the manned vehicle 11 to a prescribed point of time in the future at a maximum speed as a radius around the position P on the basis of the position P and estimates the area of a programmed traveling route 60 in the circle 70 as the existence range of the vehicle 11. The unmanned vehicle 10 judges whether its own vehicle position interferes with the circle 70 or not.