The purpose of this study was to quantitatively analyze the stress and deformation that occur in plastic ankle-foot orthoses (PAFOs) during walking after it is trimmed. First, PAFOs with incorporated sensors were individually prepared for 2 patients with hemiplegia. Mechanical data were then obtained while individuals wore the PAFOs during walking. Here we report the results of mechanical data and finite element analysis of trimmed plastic ankle-foot orthoses worn by two patients with left-hemiplegia. The results could provide prosthetists with some suggestions for forming orthoses.