Provided are a heat-fusible fiber having excellent heat resistance, flame retardancy and dimensional stability; a fiber structure comprising the heat-fusible fiber; and a molded article produced by applying a heat fusion treatment to the fiber structure and having excellent heat resistance. The heat-fusible fiber comprises an amorphous PES type polymer (A) not substantially having a melting point and an amorphous PEI type polymer (B) in the mixture ratio (weight) of (A)/(B)=5/95 to 95/5, the fiber having a single glass transition temperature in the range between 80° C. and 200° C., and being amorphous. The fiber structure comprises 10% by weight or higher of the amorphous heat-fusible fiber. The molded article comprises at least a fiber structure comprising 10% by weight or higher of the amorphous heat-fusible fiber, to be fusion-bonded at a temperature higher than the glass transition temperature of the amorphous heat-fusible fiber.