An ultrasonic probe (2) comprises a cMUT chip (20), which has a plurality of vibration elements whose electromechanical coupling coefficient or the sensitivity changes depending on a bias voltage, and transmits/receives an ultrasonic wave; an acoustic lens (26) provided on the ultrasonic wave radiation side of the cMUT chip (20); a backing layer (22) provided on the back side of the cMUT chip (20) for absorbing propagation of the ultrasonic wave; an electric wiring portion (flexible substrate (72)), which is provided from the peripheral portion of the cMUT chip (20) to the side face of the backing layer (22) and has a signal pattern connected with the electrode of the cMUT chip (20) arranged thereon; and a housing (ultrasonic probe cover (25)) for containing the cMUT chip (20), the acoustic lens (26), the backing layer (22) and the electric wiring portion (flexible substrate (72)). A ground layer (conductive film (76)) of ground potential is provided on the ultrasonic wave radiation side of the cMUT chip (20).