A control device of a motion support device that can quickly and appropriately support a predetermined motion of a user wearing the motion support device when the user performs the predetermined motion is provided. A control device estimates whether a user is in a standing state, calculates an x-axis speed V_Wx of a waist part of the user M and the absolute value VA_Wx thereof, estimates that the user has started a crouching motion from the standing state if V_Wx<；0 and VA_Wx>；Vjud1, and controls the walking assist device such that the crouching motion is supported if the user is estimated to have started the crouching motion.
