Disclosed is a resin composition having an excellent balance between shortness of curing time and longness of pot life. The resin composition contains (A) an organopolysiloxane having an alkenyl group, (B) an organopolysiloxane having a silicon atom-bonded hydrogen atom, (C) a hydrosilylation catalyst, (D) a silane coupling agent and (E) an unsaturated dicarboxylic acid ester. The component (B) contains (B-1) an organopolysiloxane having a molecular weight of not less than 5,000 but not more than 50,000 and (B-2) an organopolysiloxane having a molecular weight of not less than 100 but not more than 5,000, and the ratio of (B-2) to (B-1) is preferably not less than 0.01% by mass but not more than 20% by mass.