Provided is a curable resin composition for obtaining a cured product that can satisfy both high heat resistance and high adhesiveness to metal, a cured product thereof, and methods of producing the curable resin composition and the cured product, and a semiconductor device using the cured product as a sealant. A curable resin composition containing (A) a multifunctional benzoxazine compound having two or more benzoxazine rings, (B) a multifunctional epoxy compound having at least one norbornane structure and at least two epoxy groups, (C) a curing agent, (D) a triazole-based compound, and optionally (E) a curing accelerator and (F) an inorganic filler, a cured product thereof, and methods of producing the curable resin composition and the cured product. A semiconductor device in which a semiconductor element is disposed in a cured product obtained by curing a curable resin composition containing components (A) to (D), and optionally components (E) and (F).