An apparatus for manufacturing a transformer core includes a drawing which draws magnetic sheet materials in parallel from winding bodies. A cutter cuts the sheet materials at predetermined positions substantially simultaneously to form sheets each with a different length. An overlapping unit forms a block-shaped laminate by laminating the cut magnetic sheet materials in length and forms a resultant laminate by laminating the formed block-shaped laminates. An annulation unit forms an annular structure of the resultant laminate so that the longer block-shaped laminate forms the outer annular portion and the shorter block-shaped laminate forms the inner annular portion. Both ends of the magnetic sheet materials are abutted or overlapped to locate the abutted or overlapped portions at annularly different positions between adjoining layers of the magnetic sheet materials. A control unit controls the drawing unit, cutter and overlapping unit.