This invention is intended to improve the heat resistance of PET bottles from a material aspect. A technical problem of this invention is to find a polyester resin which is suitable for heat and pressure resistant plastic bottles and which does not eat into productivity and is available at a low cost. The object of this invention is to provide a heat and pressure resistant plastic bottle that can be manufactured at a low cost and has pressure resistance at a high temperature and high impact strength. The means of fulfilling this object is a polyester resin comprising a major part of ethylene terephthalate units and containing at least one of minor copolymerizable components selected from a group consisting of isophthalic acid, cyclohexane dimethanol, and diethylene glycol, wherein three minor copolymerizable components have total content less than 3 mol. %.