An embodiment of this movable body assistance device is equipped with: a contact-receiving body provided on a support or a movable body that moves relative to the support; a substrate supported on a rail provided on the support or the movable body that moves relative to the support; suspension vehicles, which are equipped with a base provided on the other of the support or the movable body and with rollers supported on the base and capable of rotating within the rail, and which suspend the other of the support or the movable body so as to be capable of moving on the rail; a contacting body, which is capable of moving reciprocally in a first direction with respect to the substrate and is constructed so as to be capable of engaging and disengaging from the contact-receiving body; a biasing mechanism that biases the contacting body; and a connecting part that connects the substrate in an oscillating manner with respect to the bases of the suspension vehicles.