a resin composition which is capable of forming a film that has excellent heat resistance and slidability / bendability ; a protective film for circuits , which uses the resin composition ; and a dry film or the like which comprises the protective film are provided . other aspects are a circuit board and a multilayer circuit board , each of which has excellent heat resistance and slidability / bendability . furthermore , a protective film for circuit boards is provided , which is arranged in contact with a circuit of a printed wiring board , and contains a polyoxazolidone resin that has a weight average molecular weight of 3 × 10 4 or more .