An ultrasonic probe is disclosed which includes a cMUT chip having a plurality of vibration elements whose electromechanical coupling coefficient or sensitivity is changed according to a bias voltage and transmitting and receiving ultrasonic waves, an acoustic lens arranged above the cMUT chip, and a backing layer arranged below the cMUT chip. An electric leakage preventing unit is provided at the ultrasonic wave transmission/reception surface side of the acoustic lens or between the acoustic lens and the cMUT chip. The electric leakage preventing unit can be, for example, an insulating layer such as a ground layer. Such a structure makes it is possible to provide an ultrasonic probe capable of preventing electric leakage from the ultrasonic probe to an object to be examined so as to improve the electric safety and an ultrasonic diagnostic apparatus using the probe.