A variable-stiffness actuator (10) that is to be installed in a flexible member and configured to provide different stiffnesses to the flexible member includes a shape-memory member (20) configured to transit in phase between a first phase and a second phase. The shape-memory member (20) takes a flexible state in which the shape-memory member is easily deformable by an external force when the shape-memory member is in the first phase, so as to provide lower stiffness to the flexible member. The shape-memory member (20) also takes a rigid state in which the shape-memory member tends to take a memorized shape memorized beforehand against an external force when the shape-memory member is in the second phase, so as to provide higher stiffness to the flexible member. The variable-stiffness actuator (10) further includes a conductive inducing member (30) that induces phase transition of the shape-memory member between the first phase and the second phase, and a conductive member (70) electrically connected to the inducing member (30). The conductive member (70) is arranged around an outside of the inducing member and physically protects the inducing member.
