In this paper, the boom structure of a telescopic boom-type forklift truck was analyzed using ANSYS, a finite element analysis program. As a result, 494.22 MPa exceeded 456.08 MPa, allowable stress of the material, in the second boom. Thus, structural analysis was performed by reinforcing the thickness of the boom and stress was reduced. The experiment was conducted by selecting four factors of the thickness of the boom T1, T2, T3, and T4. Through response surface analysis, the curvature of the factors for stress was confirmed, and T1 was the most influential factor. Through regression equations from the variance analysis of each response, response maximization was performed to optimize mass and stress. As a result, 467.65 MPa was predicted. This exceeded allowable stress of 456.08 MPa. To obtain the result that does not exceed allowable stress, the mass was fixed at 118 kg, the initial value, and multiple response optimization was performed to limit target value and minimize stress. As a result, 432.96 MPa was expected to occur, and structural analysis resulted in 428.87 MPa stress demonstrating 13.22% reduction of stress compared to the existing model, and it is safe because allowable stress was less than 456.08 MPa.