PURPOSE: To form a compact coil having an excellent space factor by providing a pre-winding roller, which is interlocked with a coil former pulley between the coil former pulley and a guide roller, sequentially forming a curved part that is to become the winding around an electric wire, and winding the electric wire around the coil former having a quadrangle cross section in tight contact without a convex part.

CONSTITUTION: A coil former 2 having the rectangular cross section is fixed to a coil former pulley 3 having the diameter D. A sliding part 6, which is slide in the vertical direction with respect to a fixed part 5, is provided between the coil former 2 and a guide roller 4. A pre-winding roller 7 is supported so that the roller is freely rotated. A crank pulley 8 having the diameter (d), which is 1/2 of the diameter D of the coil former pulley 3, is provided beneath the sliding part 6. The pre-winding roller 7 lifts an electric wire 1 twice during the two rotations of the coil former 2. A curved part 11 is intermittently formed and sequentially brought into tight contact with side surface parts 2A and 2A' of the rectangular coil former 2. When the cross section of the coil former 2 is square, the diameter (d) of the crank pulley 8 is made to be 1/4 of the diameter D of the coil former pulley 3.