To produce an easy-peel sealing material enabling the heat-sealing of a plastic plate and plastic vessel at a low temperature and having excellent retort resistance by using a crystalline polyester having respectively specific glass transition temperature and melting point.

The objective material is composed of a polyester resin composition composed mainly of a crystalline polyester having a glass transition temperature of ≤0°C and a melting point of 120-200°C. The composition is preferably composed of (A) 97-80 wt.% of the crystalline polyester and (B) 3-20 wt.% of a polyolefin resin (e.g. polyethylene). The composition may be incorporated with an additive, e.g. a slipping agent such as silica.