An alarm controller generates an alarm output instruction when an own vehicle state determination unit determines that an own vehicle intends to cross the opposite lane at an intersection, and the object state determination unit determines that an oncoming vehicle or a person exists or moves in a direction in which the own vehicle crosses the opposite lane at into the intersection. A shift position detector detects a shift lever position. When the shift position detector detects that a shift lever is in a parking position or a reverse position, the alarm controller does not generate the alarm output instruction.