A simulation study for finding purity changes of extract and raffinate as well as the best purity of (S)-ketoprofen in simulated moving bed (SMB) was performed with changing parameters of $m_2$ and $m_3$ from triangle theory. Aspen simulator allowed separation process simulation of (R)- and (S)-ketoprofen in SMB and compared 4-bed SMB and 8-bed SMB based on the same Henry constant and mass transfer coefficient. The 4-bed SMB consisted of 4 columns (200 mm of length, 10 mm of diameter) and the 8-bed SMB constructed by 8 columns (100 mm of length, 10 mm of diameter), and therefore total column length was made the same as 800 mm. Considering purities of both (R)-and (S)-ketoprofen, both 4-bed SMB and 8-bed SMB had the best purity when $m_2$ and $m_3$ were on 12.0 and 13.0 in the center of triangle. Taking only (S)-ketoprofen into account, 4-bed SMB as well as 8-bed SMB had the best purity when $m_2$ and $m_3$ were on 10.9 and 12.6 in the left outside triangle, and their purities were 93.3 % for 4-bed SMB and 96.9 % for 8-bed SMB.