To provide a low combustible non-halogen type water sealing material excellent in water cut-off properties.

A water sealing material with a density of 15-40 kg/m³ is formed from a polyurethane foam raw material including a polyol component, isocyanate, a foaming agent, a catalyst and a water repellent agent. In 100 pts.mass of the polyol component, 80-100 pts.mass of a hydroxy group-terminated prepolymer obtained by a reaction of polyetherpolyol and isocyanate is included. The water repellent agent is at least one selected from a group comprising polybutadienepolyol, polybutadiene hydrogenated polyol, polyisoprenepolyol and polyisoprene hydrogenated polyol. A non-halogen, non-condensed type phosphoric ester liquid at normal temperature is included by 6-13 pts.mass based on 100 pts.mass polyol component as a flame retardant. An isocyanate index is made as 100-150.