Provided is a motion transmission mechanism 30 of a limb motion support device 1A configured so as not to transmit the movements of a pair of braces 10R and 10L attached to right and left legs to spring members 20R and 20L in a state where the bending degrees of the right and left legs are smaller than a predetermined bending degree in the case where both of the right and left legs equipped with the braces 10L and 10R are bent from a stretched state and configured to transmit the movements of the braces 10L and 10R to the spring members 20L and 20R via a wire 31 after the bending degrees of the legs increase to be larger than the predetermined bending degree.