PURPOSE: To enable proper alarming and the like in accordance with the classifi cation of a detecting object by providing a means to identify whether a detected object is stable solid or moving body, and a means to judge whether it should alarm in the case the detected object is identified to be a moving body on the same lane.

CONSTITUTION: By comparing the velocity of the self-car and that of a detected object using a obstacle identifying circuit 50, whether the detected object is a stable solid or a moving body. In the case a stable solid is identified, the circuit 50 judges whether the detected object is a walllike object in the front. Also, in the case a moving body is identified, it judges whether the body is running on the same lane. Based on this classification result, the circuit 50 judges following a predetermined program whether an alarm should be done. That is, in the case either of a walllike object existing in the front or a vehicle running on the same lane is identified, it alarms with such a means as to process with displaying and to supply signal to a brake system and the like, and the device executes a more proper process coinciding with the running circumstances.