A knee-ankle-foot orthosis in accordance with the present invention can smoothly shift from the stance phase to the swing phase thereof. Namely, the knee-ankle-foot orthosis capable of securely locking a patient's knee in a desired angular position thereof with a load of his body weight, and immediately shifting his knee to the unlocked state without requiring any extra motion when the load disappears is provided. As shown in FIG. 1, the speed of the rotation of a knee axis gear 23 adapted to transmit the rotation of a knee axis 21 is increased by eight times with a speed increasing gear train 25, and is transmitted to a brake drum 41. A wire 31 wound around the brake drum 41 is connected to first and second levers 27 and 28 as load detecting members. When a foot holding portion 18 contacts the ground and the first lever 27 is stepped down, the wire 31 is pulled downwardly with a load of his body weight, whereby brakes are applied. The brake torque is increased by eight times, and is transmitted to the knee axis 21. Consequently, even with a small force due to the load of his body weight, the knee-ankle-foot orthosis can be securely locked with a braking method to prevent giving way thereof. In addition, since the braking method is used, shifting to the unlocked state can be smoothly achieved.