A terminal-crosslinkable polyamic acid oligomer having 1) heat resistance indicated by Tg of 300 C. or more and a pyrolysis temperature of 500 C. or more, 2) toughness, and 3) capability of allowing an increase in concentration. The polyamic acid oligomer is obtained by reacting an aromatic tetracarboxylic dianhydride including 2,2,3,3-biphenyltetracarboxylic dianhydride, an aromatic diamine compound, and a reactive crosslinking agent including an amino group or acid anhydride group and a crosslinkable group in the molecule, and includes a crosslinkable group at the molecular terminal.