An ultrasonic probe includes a housing, and a plurality of piezoelectric elements radially arranged in a plane substantially perpendicular to a direction in which the ultrasonic probe is inserted into a hollow portion to be scanned. The ultrasonic probe also includes an electrical part for carrying electricity to the piezoelectric elements to thereby cause the piezoelectric elements to emit ultrasonic waves and for carrying, to an external device, electric signals generated from the ultrasonic waves reflected by the hollow portion and received by the piezoelectric elements.