A walking assist device for assisting a walking movement of a user, comprising: a waist assembly adapted to be fixed to a waist of the user; and at least one leg assembly, connected to the waist assembly, the leg assembly comprising: a thigh stand adapted to be fixed to a thigh of the user; a shank stand adapted to be fixed to a shank of the user; a sole adapted for receiving a foot of the user on an upper face of the sole; a hip joint, pivoted to the thigh stand and connected to the waist assembly; a knee joint, pivoted to the thigh stand and connected to the shank stand; and an ankle joint, characterized in comprising: a fixing plate connected to the shank stand; at least a flexible plate being a metal plate with a slight flexibility or an elastic plastic plate; and an elastic member being a spring or a compressible element formed by elastic material, wherein the flexible plate comprises a first end and a second end opposite to the first end, the first end is pivoted to the fixing plate, the second end is connected to the sole, and the elastic member is disposed at a side of the first end of the flexible plate so as to press the first end of the flexible plate for providing a friction force between the fixing plate and the flexible plate. a waist assembly adapted to be fixed to a waist of the user; and at least one leg assembly, connected to the waist assembly, the leg assembly comprising: a thigh stand adapted to be fixed to a thigh of the user; a shank stand adapted to be fixed to a shank of the user; a sole adapted for receiving a foot of the user on an upper face of the sole; a hip joint, pivoted to the thigh stand and connected to the waist assembly; a knee joint, pivoted to the thigh stand and connected to the shank stand; and an ankle joint, characterized in comprising: a fixing plate connected to the shank stand; at least a flexible plate being a metal plate with a slight flexibility or an elastic plastic plate; and an elastic member being a spring or a compressible element formed by elastic material, wherein the flexible plate comprises a first end and a second end opposite to the first end, the first end is pivoted to the fixing plate, the second end is connected to the sole, and the elastic member is disposed at a side of the first end of the flexible plate so as to press the first end of the flexible plate for providing a friction force between the fixing plate and the flexible plate. a thigh stand adapted to be fixed to a thigh of the user; a shank stand adapted to be fixed to a shank of the user; a sole adapted for receiving a foot of the user on an upper face of the sole; a hip joint, pivoted to the thigh stand and connected to the waist assembly; a knee joint, pivoted to the thigh stand and connected to the shank stand; and an ankle joint, characterized in comprising: a fixing plate connected to the shank stand; at least a flexible plate being a metal plate with a slight flexibility or an elastic plastic plate; and an elastic member being a spring or a compressible element formed by elastic material, wherein the flexible plate comprises a first end and a second end opposite to the first end, the first end is pivoted to the fixing plate, the second end is connected to the sole, and the elastic member is disposed at a side of the first end of the flexible plate so as to press the first end of the flexible plate for providing a friction force between the fixing plate and the flexible plate. a fixing plate connected to the shank stand; at least a flexible plate being a metal plate with a slight flexibility or an elastic plastic plate; and an elastic member being a spring or a compressible element formed by elastic material, wherein the flexible plate comprises a first end and a second end opposite to the first end, the first end is pivoted to the fixing plate, the second end is connected to the sole, and the elastic member is disposed at a side of the first end of the flexible plate so as to press the first end of the flexible plate for providing a friction force between the fixing plate and the flexible plate.