PURPOSE: To reduce the cost and to simplify a device by designating the coordinate position of an object on a coordinate picture with an ultrasonic sensor consisting of the combination of an ultrasonic transmitter and at least two ultrasonic receivers.

CONSTITUTION: Ultrasonic sensors 4L and 4R, a transmission circuit 6, a reception circuit 8, and a control circuit 50 are provided. The reception circuit 8 outputs reception time data related to the input of one ultrasonic receiver 4L and that of the other ultrasonic receiver 4R to the control circuit 50 in accordance with the input time of a timing signal. These reception time data correspond to the position of an object P on a coordinate picture 2. The control circuit 50 calculates the coordinate position of the object P on the coordinate picture in accordance with a first time difference between the output time of the timing signal and one reception time and a second time difference between the input time and the other reception time. Thus, the coordinate position of the object P is accurately designated in spite of the low cost and the simple constitution.