An ultrasonic probe, a charger and an ultrasonic diagnostic apparatus, and an ultrasonic diagnostic system that uses them are provided by the present invention, which comprises a detector for detecting whether or not an ultrasonic probe having a rechargeable battery or the charger for charging this is in charging state; and a controller for stopping transmitting and receiving operations of ultrasonic waves. The ultrasonic diagnostic apparatus comprises a transmitting and receiving circuit for executing the generation of a signal related to the transmission of the ultrasonic waves and the generation of the diagnostic information based on the signal related to the reception of the ultrasonic waves; a probe switching circuit for selecting one of a plurality of ultrasonic probes; and a controller for controlling the probe switching circuit in accordance with a detection signal from the detector. The ultrasonic diagnostic system comprises the above-mentioned probes, chargers and diagnostic apparatus.