Slide-ring materials (SRM) are novel polymeric elastomers which are prepared from necklace-like supramolecule, polyrotaxane, consisting of ring molecules and axial polymer. By cross-linking rings of polyrotaxanes, axial polymer chains are connected via ring molecules which can slide on polymer chains. The slidability of the cross-linking points leads to softness and deformability of SRMs. In this work, we investigate the unique mechanical properties of SRMs to apply them to dielectric elastomer actuators (DEAs). From dynamic viscoelasticity measurements, we have found that SRMs exhibit entropic elasticity and low elastic modulus. The stress strain relation of SRMs under uniaxial deformation follows ideal rubber elasticity model in a wide strain range, suggesting homogeneous and reversible network deformation caused by the sliding of cross-linking points in SRMs. The ideal rubber elasticity of SRMs results in their softness and low hysteresis under large deformation, which are advantages for the application as dielectric elastomer actuators.