An actuator includes a first deformable material layer, a second deformable material layer, and an intermediate layer provided between the first deformable material layer and the second deformable material layer. The first deformable material layer includes a first deformable material containing a first stimulus-responsive compound, which changes its molecular structure and also its color tone according to an oxidation-reduction reaction, a first polymeric material, a first electronically conductive substance having a light transmitting property, and a first electrolyte. The second deformable material layer includes a second deformable material containing a second stimulus-responsive compound, which changes its molecular structure and also its color tone according to an oxidation-reduction reaction, a second polymeric material, a second electronically conductive substance having a light transmitting property, and a second electrolyte. The intermediate layer inhibits electron transfer between the first deformable material layer and the second deformable material layer.