Disclosed is a gasket-forming material for hard disks, which enables to obtain a gasket capable of improving reworkability of a cover plate and a base plate of a hard disk device. Also disclosed is a gasket produced by using such a gasket-forming material. Specifically disclosed is a gasket-forming material for hard disks, which is characterized by containing (A) an energy ray-curable liquid urethane oligomer having a polymerizable unsaturated group, and (B) a monofunctional (meth)acrylic monomer whose cured product has a glass transition temperature (Tg) of from -70 DEG C to 20 DEG C. Also specifically disclosed is a gasket for hard disks, which contains a cured product obtained by curing such a gasket-forming material through irradiation of an energy ray.