To provide an inner pipe connecting method for a double-pipe exhaust manifold capable of lowering the cost by reducing the machining process.

The connecting end part in one first inner pipe 31 constituting an inner pipe is formed cylindrical, and the inside diameter of the connecting end part in the other second inner pipe 32 is substantially equal to the outside diameter of the first inner pipe 31. Axial slits s and s are formed at least in one portion in the circumferential direction of the connecting end part, and fixed pieces 32c and 32d are respectively extended outward substantially parallel at designated spaces from both side edge parts of the slits s and s. With the cylindrical connecting end part of the first inner pipe 31 inserted in the connecting end part of the second inner pipe, both fixed pieces 32c and 32d of the second inner pipe 32 are pressed and welded by spot welding, thereby connecting the first inner pipe 31 and the second inner pipe 32 to each other tightly without play in the state of expanding and contracting in the axial direction.