Leg cores 1a are clamped with leg core clamping metal fittings 3 and united with a plurality of leg core clamping bands 4. Yokes 1b are arranged in parallel with the stacking direction of the leg cores 1b, clamped with yoke clamping metal fittings 5 having a width equal to the minimum width of the yokes 1b, and united with a plurality of yoke clamping bands 6. Winding 2 inserted into the leg cores 1a, meanwhile, couples winding clamping square type steel pipes 7a and 7b arranged above and below the winding 2, above and below the leg core clamping metal fittings 3, and spacers 8 are arranged between the winding clamping square type steel pipes 7 and the winding 2 and adjusted to clamp them. The winding clamping square type steel pipes 7a and 7b are composed of members having excellent rigidity and small mass.