An ultrasonic probe (10) of a radial scan type mountable on an ultrasonic observation apparatus (11), which inputs and outputs M numbers of signals in parallel, comprises the following: N (N>M) numbers of ultrasonic transducers (12) disposed on an outer periphery of a tip, and grouped into plural sensor element groups (40a, 40b, 40c and 40d) activated in sequence, each of which has M numbers of ultrasonic transducers N numbers of first signal lines (16) respectively connected to the N numbers of ultrasonic transducers for transmitting drive signals and echo signals M numbers of second signal lines (18) connected to the ultrasonic observation apparatus and a multiplexer (17) disposed between the first signal lines and the second signal lines, which selectively switches M numbers of the first signal lines for respectively connecting to the second signal lines according to the sensor element group to be activated.
