Systematic investigations of Ga1−xMnxAs grown on InP with different Mn concentrations have been conducted using magnetic circular dichroism (MCD) in reflection mode. The MCD spectrum of Ga0.97Mn0.03As/InP was decomposed into two dispersion curves originating from E1 and E1 + Δ1 optical transitions using the energy derivative of a Gaussian function. The Zeeman splitting energy E1 at the L critical point (0.6 meV) of ferromagnetic Ga0.97Mn0.03As/InP was estimated using a rigid band shift model. Based on the relationship between E1 and E0 (Γ critical point) observed in Cd1−xMnxTe dilute magnetic semiconductor (DMS), the Zeeman splitting energy E1 (9.6 meV) of ferromagnetic Ga1−xMnxAs/InP was calculated. In addition, it was established that the peaks in the MCD spectra at L critical points shift toward the lower energy side as the Mn concentration is increased, and the observed shift saturates for Mn content of x = 0.001. Furthermore, the measured absorption spectra for Ga1−xMnxAs/InP did not show noticeable peak shifts with increasing Mn content. This suggests that the s, p–d exchange interaction induced in Ga1−xMnxAs/InP has localized nature due to the presence of a Mn rigid sphere of influence.