In this study, shape optimization was performed by changing the blade angles of the impeller and diffuser, which are key components of a 100 kW multi-stage centrifugal pump. The specifications of the initial model of the impeller are 135.6 m of head at 250 ㎥/h of flow rate, 3600 r/min of revolution, and 187 ㎜ of impeller outer diameter. Using ANSYS BladeGen, the shape was regenerated to enable blade coordinate data and angle change, and flow analysis was performed with ANSYS CFX. Discrete Latin Hypercube Design (DLHD) and Sequential Approximate Optimization (SAO) were applied as shape optimization techniques. Efficiency was set to the maximum as the design objective condition, and optimization was performed by minimizing the shaft power as the constraint condition. Compared to the initial model, the optimized model was found to increase head by 8.57%, axial power by 7.13%, and efficiency by 1.35% at a flow rate of 250 ㎥/h.