To provide a composite resin composition with which even a wet position can be coated or filled and which shows excellent water proof, is cur able in a short time and does not cause fluidization and flow-down after coating and filling to avoid dropping.

The composite resin composition is obtained by mixing at least a powder aggregate, a hydraulic setting material, an epoxy-based synthetic resin and a curing agent for the resin wherein the epoxy-based synthetic resin is mixed with the curing agent for the resin in use, the mixing ratio being predetermined, the powder aggregate contains a fine garnet microcrystal and has an average diameter of 5 to 1,200 μm, the hydraulic setting material is a hydraulic setting cement composed of silicone dioxide, aluminum oxide, ferric oxide, calcium oxide, magnesium oxide and sodium oxide, each ratio being predetermined, the epoxy-based synthetic resin contains talc, the amount of the talc being predetermined based on a modified epoxy resin, and the curing agent for the resin contains a talc, the amount of the talc being predetermined based on an amine acid salt and an amide acid salt.