Abstract: An insulating polymer material composition of the environment-conscious type which is obtained by using a renewable resource and a waste material as starting materials is provided. A vegetable oil-origin epoxy resin and a plant-origin polyphenol are mixed and the obtained mixture is subjected to a heat treatment, with which a liquid epoxy resin composition which is a compatibilized blend of the vegetable oil-origin epoxy resin and the plant-origin polyphenol is provided. To this liquid epoxy resin composition, coal ash and a silane coupling agent are added followed by mixing. Further, an additive such as a curing accelerator is added thereto, followed by a heat treatment, thereby obtaining an insulating polymer material composition. As the coal ash, it is preferable to use fly ash. It is also preferable to use a silane coupling agent having epoxy group.