PURPOSE: To heat a waterdrop being a medium to high temp. without heating the whole of a sample or a probe by providing a heater part to the periphery of an acoustic lens and bringing a piezoelectric element, the acoustic lens and the heater part to an integrated structure.

CONSTITUTION: A heater part 7 is arranged to the periphery of an acoustic lens 2 and the leading end thereof protrudes from the leading end of the lens 2 on the arranging side of a sample 4. At first, a current is allowed to flow to a lead wire 11 from a terminal part 9. This current flows to a heating wire 7A to generate heat and the lens 2 is heated and a waterdrop 3 is heated to be raised to about 60°C in its temp. Thereafter, voltage for driving a piezoelectric element 1 is applied to a lead wire 10 from a terminal part 8 to emit an ultrasonic wave (frequency: about 100 - 2000 MHz) which is, in turn, sent to the sample 4 through the waterdrop of 60°C. The reflected ultrasonic wave from the sample 4 is sent to the outside as a reflection signal through the element 1 and the terminal part 8. By this method, the waterdrop 3 can be rapidly heated to high temp. and the attenuation of a sonic wave is reduced. Further, the damage of the leading end of the lens 2 during measuring operation can be eliminated.