In the obstruction detection apparatus incorporated in a vehicle (11), ultrasonic wave transmitter/receiver (16 to 19 171) for changing a combination of transmitting of ultrasonic waves and of receiving of reflected ultrasonic waves, a CPU (20) calculates a distance between the vehicle (11) and an obstruction and stores data corresponding to the calculated distance into the distance table (23), and the LC display device (27) displays the obstruction on display bars of a lattice shape corresponding to the data stored in the distance table (23), and a buzzer (26) sounds an alarm for a driver.