PURPOSE: To manufacture the titled covering material capable of forming a film with superior flexibility at a high curing speed by blending modified polybutadiene formed by a specified method with a compound having a polymerizable C=C bond and a polymn. initiator.

CONSTITUTION: Modified polybutadiene having two or more introduced (meth)acryloyl groups is formed by reacting a compound having an epoxy group and a (meth)acryloyl group such as glycidyl acrylate or a compound having two or more epoxy groups such as bisphenol A type epoxy resin and (meth)acrylic acid with hydrogenated 1,2-polybutadiene having two or more carboxyl groups. Said modified polybutadiene (A) is blended with a compound (B) having a polymerizable C=C bond such as tetrahydrofurfuryl acrylate and a polymn. initiator (C) such as benzyl methyl ketal.