An ultrasonic scanning instrument uses a probe formed by arranging a plurality of oscillator pieces aligned on a flexible base plate. The oscillator pieces each transmit ultrasonic waves into a target body and receive reflected waves. Sensors are attached to the flexible base plate to detect degrees of flexure of the base plate. The flexible base plate becomes curved according to the curved contact surface of the target body and its degree of flexure measured by the sensors is incorporated into a sectional view displayed on a display device.