We have developed a new method for the determination of the crystal orientation of CuInSe2 by Raman spectroscopy. The single crystal of CuInSe2 has a (112) natural surface. On this surface we often observe slip lines, which construct a triangular shape. However, it is difficult to identify which corner is the projection of the c axis. We established a new method to identify the c direction by using Raman spectroscopy. This method is also effective for small single crystals down to the size of 1 μm.