Provided is a novolac resin having excellent developability, heat resistance, and dry etching resistance, and a resist film. A novolac resin includes a cyclic novolac resin (A) having a molecular structure represented by Structural Formula (1): (in the formula, α is a structural moiety (α) represented by Structural Formula (2): n is an integer of 2 to 10), in which at least one of X's present in the resin is any one of a tertiary alkyl group, an alkoxyalkyl group, an acyl group, an alkoxycarbonyl group, a hetero atom-containing cyclic hydrocarbon group, and a trialkylsilyl group, at least one of the structural moieties (α) present in the resin is a structural moiety (α1) in which l is 1, and at least one thereof is a structural moiety (α2) in which l is 2.