A gel actuator includes: a gel having a projected part made of an inductive high-polymer material; a positive electrode disposed so as to be in contact with a top of the projected part; and a negative electrode disposed in a position sandwiching the projected part in a height direction in cooperation with the positive electrode. When voltage is applied between the positive and negative electrodes, creep deformation occurs so that the projected parts adhere to the positive electrode side, and the gel contracts in the thickness direction.