According to on embodiment, a power supply circuit is provided in a main body and generates operating voltages for various electric circuits in the ultrasonic probe. Signal lines SL1 connects the power supply circuit to the electric circuits by way of the probe connector, to supply operating voltages from the power supply circuit to the electric circuits. A voltage monitoring circuit is provided in the main body and monitors voltages supplied to the electric circuits, utilizing the input voltage from the ultrasonic probe. To supply input voltages to the voltage monitoring circuit, signal line SL2 branches from signal lines SL1 in the ultrasonic probe and connects the electric circuits and the voltage monitoring circuit to each other by way of the probe connector.