An ultrasonograph contains a probe provided with a transmitting/receiving ultrasonic transducer at the center thereof, and the probe has a transmitting ultrasonic transducer and a receiving ultrasonic transducer which are symmetrically movable with respect to the transmitting/receiving ultrasonic transducer. Contacting the probe with the skin of a diagnosis area, a direction of the probe is adjusted to be perpendicular to the diagnosis object using echo signals of the transducer. Then the echo signals of the transmitting ultrasonic transducer and the transmitting/receiving ultrasonic transducer, and a distance between the ultrasonic transducers are processed to obtain a signal intensity. Results are displayed on a display to indicate the thickness, hardness of an articular cartilage, and a surface condition thereof visually so that it is possible to diagnose the articular cartilage without inserting a probe into the cavitas articulare.