The fit of prostheses and orthoses is important, because, if the fit is inadequate, patients may feel uncomfortable. A poor fit can cause difficulty in gait, and, in the worst cases, it can cause inflammation. An evaluation system for checking the fit that utilizes human models has been developed. Human models of the residual limb and lower thigh with bone, muscle, and fat were composed. These models were used to evaluate the fit of the transfemoral socket and ankle foot orthosis (AFO) by dynamic finite-element analysis (FEA). For the transfemoral socket, insertion simulation was performed, and the validity of the fat part and pressure distribution of the residual limb were evaluated using magnetic resonance imaging and the force measured by sensors built in the socket. For the AFO, gait simulation of the stance phase was performed, and the transition of strain was compared with the measured result by the 3D-printed AFO, on which strain gauges were pasted. In addition, by performing topological optimization, the weight of the AFO can be reduced by maintaining the stiffness of the AFO. The results indicate the qualitative validity of dynamic FEA for analyzing the prosthesis socket and AFO using a human leg model.