PURPOSE: To obtain a surface wave probe by which surface waves are propagated efficiently to an object to be measured and a flaw detector or the like is made small-sized, by providing a surface wave exciting electrode and a receiving electrode on a piezoelectric substrate where both sides of a recessed groove are used as the first and the second contact parts which are in contact with the material to be measured.

CONSTITUTION: When a prescribed exciting signal is applied to an exciting electrode 15 to generate surface waves on a substrate 11, surface waves reach the rear face of the substrate 11 round one circumferential edge of the substrate 11 as shown in figure by arrows and are transmitted to an object 13 to be measured in the first contact part 141 and are propagated on the surface of the object 13 just under the recessed groove 12 and are transmitted again to the substrate 11 in the second contact part 142. Surface waves which are returned into the substrate 11 through the object 13 to be measured in this manner and are propagated round the other circumferential edge are converted to an electric signal by a receiving electrode 16 and are detected. Thus, existence of flaws and distortion on the surface of the object 13 to be measured just under the distortion on the surface of the object 13 to be measured just under the recessed groove 12 is detected, and physical properties such as an acoustic velocity on this surface are measured.