Provided is a walking motion assisting device capable of assisting a leg of an agent in walking motion to alleviate an assisting burden or eliminate an assisting necessity by a caregiver. According to the walking motion assisting device (1), the value of a persistent energy input term (ζ0) contained in a simultaneous differential equation denoting a second model configured to generate a second motion oscillator (φ1) is adjusted so as to limit a landing position (x) of a leg of the agent in a specified range [x1, x2]. Further, the motion state of the leg is recognized on the basis of a variation mode of a second oscillator (ξ2), and on the basis of the recognition result, the relative motion between the thigh and crus of the leg around the knee joint is assisted.
