To provide an imide oligomer which is easy to thermoform, which has excellent heat resistance after being heat cured at a low temperature, and which shows a large breaking elongation.

An imide oligomer has three or more molecules per tetramer of 2,3,3',4'-biphenyl tetracarboxylic dianhydride of a non-axisymmetric aromatic acid anhydride, three or more molecules of 1,4-bis(4-aminophenoxy)benzene, and only one or less molecule of 3,4'-diaminodiphenyl ether, 1,3-bis(3-aminophenoxy)benzene or 1,3-bis(4-aminophenoxy)benzene, independently or in the combined state; and the crosslinkable end thereof comprises 4-(methyl ethynyl) phthalic anhydride residue.