PURPOSE: To make ultrasonic wave receiving/transmitting surfaces flush each other on the same flat plate by arranging electrodes in areas of a piezo-electric element board as demarkated with grooves to form independent wave transmitter/receivers.

CONSTITUTION: Conductors 11 are deposited beforeahead in individual diced pieces 10' formed on a piezo-electric element 10 by dicing it. The conductors 11 thus deposited serve as positive electrodes for respective diced pieces 10' as demarked by dicing to which a cable 18 is connected. Grooves 12 by dicing are provided to prevent horizontal vibration of the diced pieces 10'. A wave transmission signal is applied to the positive electrodes of the diced pieces 10' and ultrasonic waves are transmitted separately from the diced pieces 10'. This permits ultrasonic wave transmitting/receiving surfaces to flush each other on the same plane.