PURPOSE: To provide an acoustic lens which has a short focal depth and can obtain excellent depth resolution.

CONSTITUTION: A piezoelectric transducer 12 is disposed along a spherical surface 11c to radiate a sound wave of a converging spherical wave state into a lens rod 11 and to once converge the wave in the rod 1. An infinitesimal coupling part 11b for passing the wave only in a predetermined range near a converging point is provided at the point of the wave to be radiated from the transducer 12 to pass only the wave reflected at a predetermined focal surface therethrough to be guided to the transducer 12, and the wave reflected from a non-focal surface is limited by the part 11b to eliminate its arrival of the transducer 12.