We fabricated an ultrasonic probe with a through hole for needle puncture. The probe consists of a ring-shaped transducer around the hole for detecting needle tip and 12 fan-shaped transducers around the ring-shaped transducer for observing a lesion area. A B-mode image was obtained for inserting a needle into the pig liver. We investigated the phase of signals from the needle tip using an ultrasonic probe having separated elements of transmitter and receiver. From the experimental results the detection principle of the needle tip was explained by edge waves.