In this study, a material model of human skeletal muscle which represents force exertion and anisotropy due to muscle contraction was developed. The mechanical properties of the skeletal muscle were divided into passive and active stresses. The passive stress was caused by external deformation, while the active stress was generated by the muscle contraction. The strain energy function proposed by Arya and Singh was used to model skeletal muscle [1]. In this model, the total deformation gradient tensor was divided into elastic and active component to represent the passive and active stress. The active deformation was determined by the degree of muscle activity and the orientation angle of the muscle fibers, while the elastic deformation is determined indirectly from the total deformation gradient tensor and the active deformation gradient tensor. The applicability of the proposed material model was investigated by varying the muscle activity and the fiber orientation.