Single crystal of nonlinear optical crystal CsB₃O₅ (CBO) which has good properties for deep ultra-violet (UV) generation was investigated, and some optical properties were measured for the first time. In this report, the growth conditions were experimentally established. Single crystals with good optical homogeneity were obtained when the rotation rate of crystal was faster than 30 rpm. This phenomenon was explained by considering growth phenomena of segregation effect. Large single crystals were grown by a top seeded solution growth with the established conditions. The size of one of these was a×b×c=45×41×44mm³. Optical absorption edges at UV and IR regions were measured quantitatively to be 168 nm and 3400 nm.