PURPOSE: To make the backing effect for a piezo-electric element constant and to reduce variances of sending and receiving efficiencies of ultrasonic wave by making between the piezo-electric element and a backing material devoid of an adhesive layer.

CONSTITUTION: The probe 11 has a piezo-electric element 1 as a ultrasonic vibrator, and a molded backing material 6 is provided on the back of the piezo-electric element 1. To manufacture the probe, a piezo-electric element 21 is set on the bottom of a molding frame 22 and an epoxy resin 23 is filled on its. In the next process, at about an hour after molding the epoxy resin 23, tungsten powder 24 is mixed in an epoxy resin of the same composition as that of the epoxy resin 23, and the mixture 25 left as it is for about 30min is poured on the epoxy resin 23, and heated and cured in an atmosphere of about 50°C. During curing, the tungsten powder settles down slowly in the cured epoxy resin 23 and disperses. Thus, an acoustically continuous backing material 6 is formed. A piezo-electric element 1 having a backing material 6 is formed by unifying the block of piezo-electric element 21 and backing material 23 thus formed.