PURPOSE: To miniaturize the iron core type reactor by arranging an iron core leg, to which a block iron core is set up, outside winding and disposing an iron core leg with no air gap into the winding.

CONSTITUTION: An iron core main leg 8 is arranged inside the winding 1, and a yoke 3 is disposed to the upper and lower sections of the iron core leg 8. The block iron cores 10 are arranged to the side section of the yoke 3, and disposed alternately together with the air gaps 5, and a side-section iron core leg 9 is formed. Magnetic flux density can be increased up to a value close to saturation flux density because the iron core main leg 8 has no air gap. Structure need not be formed in a circle by arranging the iron core leg with the air gaps outside the winding 1, and the reactor can be simplified. Accordingly, the iron core legs and the diameter of the winding can be made small, and the iron core type reactor can be miniaturized.