To provide a polyimide resin capable of being processed into a flexible metal-clad laminate excellent in high-temperature processability and good in adhesion.

The polyamic acid is obtained by polymerizing (A) at least one tetracarboxylic acid dianhydride selected from among 3,4,3', 4'-, 2,3,3', 4'-, and 2,3,2', 3'-biphenyltetracarboxylic acid dianhydrides; (B) at least one linear acid dianhydride selected from pyrromellitic acid dianhydride and 2,3,6,7- and 1,4,5,8-naphthalenetetracarboxylic acid dianhydrides; (C) 2,2'-dimethyl-4,4'-diaminobiphenyl and/or p-phenylenediamine; and (D) at least one diamine component selected from 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 3,3'-diaminodiphenyl ether, and 3,4'-diaminodiphenyl ether.