Provided are a polyurethane-modified epoxy resin composition having satisfactory operability of processing, such as casting or impregnation, in a composition state, a production method therefor, and a composition thereof. The polyurethane-modified epoxy resin is obtained by modifying a secondary hydroxyl group-containing bisphenol-based epoxy resin (a) having an epoxy equivalent of from 150 g/eq to 200 g/eq and a hydroxyl equivalent of from 2,000 g/eq to 2,600 g/eq with a medium to high molecular weight polyol compound (b) having an Mn of 200 or more, a polyisocyanate compound (c), and a low molecular weight polyol compound (d) having an Mn of less than 200 serving as a chain extender. The polyurethane-modified epoxy resin uses the epoxy resin (a) in an amount of from 20 wt % to 60 wt % with respect to the total amount of the respective components (a), (b), (c), and (d), and contains a polyurethane having the epoxy resin (a) added to each of both terminals thereof and/or one terminal thereof.

A polyurethane based asphalt composition includes an asphalt component and a polyurethane resin system that is the reaction product of an isocyanate component that includes at least one polyisocyanate and an isocyanate-reactive component that includes a cardanol-modified epoxy polyol. The cardanol-modified epoxy polyol is a reaction product of an epoxy component and an epoxy-reactive component at a ratio of epoxy groups to epoxy reactive groups from 1:0.95 to 1:5. The epoxy-reactive component includes a cardanol component.