An object of the invention is to provide carboxyl group-containing polyurethanes that have small curing warpage and can give cured products having excellent electrical insulating properties and flexibility, curable compositions that contain the carboxyl group-containing polyurethane and can give cured products having good electrical insulating properties, cured products obtained from the compositions, flexible circuit boards covered with the cured products, and processes for manufacturing flexible circuit boards. The carboxyl group-containing polyurethane is obtainable from materials including a (poly)carbonate polyol (a) that includes an organic residue derived from a dimer diol, a polyisocyanate (b) and a carboxyl group-containing polyol (c).