Provided is a resin composition for encapsulating a semiconductor which has excellent flame resistance and solder resistance, and can be manufactured at a low cost. The composition includes a phenol resin (A), an epoxy resin (B), and an inorganic filler (C). The phenol resin (A) includes at least one polymer component (A0) composed of a polymer having structural units represented by general formulae (1) and (2), and at least one polymer component (A0) is composed of a polymer having structural units represented by general formulae (1) and (2) and terminated on at least one end with an aromatic group free of polar groups and containing at least one alkyl group having 1 to 3 carbon atoms: wherein R1 and R2 are each independently a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms; each R3 is independently a hydrocarbon group having 1 to 6 carbon atoms; and a is an integer of 0 to 3 , wherein R5, R6, R8 and R9 are each independently a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms; each R4 and R7 is independently a hydrocarbon group having 1 to 6 carbon atoms; b is an integer of 0 to 3; and c is an integer of 0 to 4.