The velocities of leaky surface acoustic waves (SAWs) have been measured using a large-aperture line-focused transducer for three silicon single crystals (namely, Si-100, Si-110, and Si-111). While rotating the specimen, velocities were measured as a function of propagation direction. The slowness curves of the SAWs show good agreement with the crystal structures of the specimens. Finite element method (FEM) simulation has also been carried out for silicon crystals and the results were compared with the measurement results. The FEM results can explain the measured ones. This method has high potential for determining crystal structures. (C) 2017 The Japan Society of Applied Physics.