To provide an epoxy resin composition which has a shorter curing time and a lower curing temperature than those of existing prepregs.

This matrix resin composition is characterized by containing (a) an epoxy resin having two or more epoxy groups per molecule on the average, and (b) 2,4-di(N,N-dimethylureide)toluene as essential components, and satisfying either of conditions (i) and (ii). (i): When the matrix resin composition is heated at 150°C for 3 min, the product has a glass transition temperature of >140°C. (ii): When the matrix resin composition is heated at 80°C for 5 h, the product has a glass transition temperature of >100°C. The obtained prepreg can reach a 95% cured state at a time of about a half in comparison with the prepreg in which only a used catalyst is different. In addition, when a prepreg using the epoxy resin composition is cured at 80 to 150°C, the cured prepreg can be taken out from a mold without cooling the cured prepreg, because the glass transition temperature of the cured prepreg is higher than the curing temperature.