Abstract: A posterior upright of an ankle foot orthosis with adjustable degree of bending. A posterior upright 4 of an ankle foot orthosis 1 is provided between a heel posterior portion of a footrest portion 2 on which a foot portion is placed and a lower leg mounting portion 3 mounted on a lower leg portion below a knee. In the posterior upright 4, a plurality of FRP sheets 5a to 5c are laminated, and an upper end portion and a lower end portion of the FRP sheets are joined by heat sealing. An upper end portion 4A is a portion connected to the lower leg mounting portion 3 and a lower end portion 4B is connected to the footrest portion 2. An intermediate portion between the upper end portion 4A and the lower end portion 4B has +gaps S1 and S2 between the FRP sheets 5a to 5c.