The present invention aims to provide a composition for soft materials, which enables production of a soft material excellent in transparency, a stress relaxation property, and strength and having an elongation property that is not so much lowered even at high temperatures. The present invention also aims to provide a soft material produced using the composition for soft materials of the present invention. The present invention relates to a composition for soft materials including polyrotaxane and a radical polymerizable monomer, the polyrotaxane including a cyclic molecule, a linear molecule threading through a cavity of the cyclic molecule in a skewered manner, and capping groups that cap both ends of the linear molecule, the polyrotaxane having at least one cyclic molecule with a radical polymerizable group, the polyrotaxane having at least two radical polymerizable groups.