The invention relates to (1) a curable epoxy resin composition comprising (A) a non-gel type amine-modified epoxy resin which is obtained by reacting an epoxy resin with a polyamine and (B) at least one of boric acid and boric ester, (2) a powder form of the curable epoxy resin composition and a process for its production, and (3) a process for production of heat-resistant laminated sheets by using the curable epoxy resin composition. The invention provides (1) a curable epoxy resin composition capable of giving a cured article having a high glass transition temperature and excellent mechanical properties, (2) a powder form of curable epoxy resin composition having a high glass transition temperature, excellent mechanical properties and excellent storage stability and a process for its production, and (3) heat-resistant laminated sheets made by using the curable epoxy resin compositions and having excellent heat resistance and mechanical properties.