A thermosetting cured light-reflecting resin comprising an epoxy resin, a curing agent, a curing catalyst, an inorganic filler, a white pigment, an additive, and a release agent, wherein: the additive comprises a compound, said compound being a triblock copolymer represented by formula: wherein I is an integer of 1 to 200, m 1 +m 2 is an integer of 2 to 400, R 1 is selected from the group consisting of an alkylene group having 1 to 10 carbon atoms, R 2 and R 3 are independently selected from the group consisting of: a monovalent organic group having 1 to 10 carbon atoms including at least one of an alkyl group, an aryl group, an alkoxy group, and an epoxy group; a monovalent organic group having 1 to 10 carbon atoms including a carboxyl group; and a polyalkylene ether group having 3 to 500 carbon atoms, and R 4 is selected from the group consisting of a divalent hydrocarbon group having 1 to 10 carbon atoms and the release agent is at least one compound selected from the group consisting of an aliphatic carboxylic acid, an aliphatic carboxylic acid ester, an aliphatic polyether, a non-oxidized polyolefin, and an oxidized polyolefin having a carboxyl group, and the resin composition, after curing, has a diffuse reflectance of at least 80% at a light wavelength of 350 nm to 800 nm; and the resin composition is suitable to perform transfer molding at least 100 times continuously. the additive comprises a compound, said compound being a triblock copolymer represented by formula: wherein I is an integer of 1 to 200, m 1 +m 2 is an integer of 2 to 400, R 1 is selected from the group consisting of an alkylene group having 1 to 10 carbon atoms, R 2 and R 3 are independently selected from the group consisting of: a monovalent organic group having 1 to 10 carbon atoms including at least one of an alkyl group, an aryl group, an alkoxy group, and an epoxy group; a monovalent organic group having 1 to 10 carbon atoms including a carboxyl group; and a polyalkylene ether group having 3 to 500 carbon atoms, and R 4 is selected from the group consisting of a divalent hydrocarbon group having 1 to 10 carbon atoms and the release agent is at least one compound selected from the group consisting of an aliphatic carboxylic acid, an aliphatic carboxylic acid ester, an aliphatic polyether, a non-oxidized polyolefin, and an oxidized polyolefin having a carboxyl group, and the resin composition, after curing, has a diffuse reflectance of at least 80% at a light wavelength of 350 nm to 800 nm; and the resin composition is suitable to perform transfer molding at least 100 times continuously. I is an integer of 1 to 200, m 1 +m 2 is an integer of 2 to 400, R 1 is selected from the group consisting of an alkylene group having 1 to 10 carbon atoms, R 2 and R 3 are independently selected from the group consisting of: a monovalent organic group having 1 to 10 carbon atoms including at least one of an alkyl group, an aryl group, an alkoxy group, and an epoxy group; a monovalent organic group having 1 to 10 carbon atoms including a carboxyl group; and a polyalkylene ether group having 3 to 500 carbon atoms, and R 4 is selected from the group consisting of a divalent hydrocarbon group having 1 to 10 carbon atoms and the release agent is at least one compound selected from the group consisting of an aliphatic carboxylic acid, an aliphatic carboxylic acid ester, an aliphatic polyether, a non-oxidized polyolefin, and an oxidized polyolefin having a carboxyl group, and the resin composition, after curing, has a diffuse reflectance of at least 80% at a light wavelength of 350 nm to 800 nm; and the resin composition is suitable to perform transfer molding at least 100 times continuously.