A movement assist device includes: a motor including a stator and a rotator; two arm members connected to each of the stator and the rotator and configured to be connected to a predetermined part of a body of an equipped person; a signal acceptor configured to accept a trigger signal that triggers a driving of the motor; and a driving controller configured to drive the motor so that the two arm members expand in response to a trigger that the signal acceptor accepts a first one of the trigger signal.