A main body frame 40 of a walking assist device 1, which is to be fixed to the waist of a user, has first frames 41 to be fixed to the waist of the user, second frames 42, and connection mechanisms 43, which connect the first frames 41 and the second frames 42 such that the relative positions of the second frames 42 with respect to the first frames 41 change according to the motions of the legs of the user.