To prevent generation of displacement of transformer characteristics due to heating by bonding a laminated iron core joint part or an air gap part by a normal temperature hardness adhesive.

A center leg laminated iron core 25 is pressed into a side leg laminated iron core 30, an adhesive is charged into an air gap part, and assembling is performed. When the adhesive is charged, an acryl 2-liquid normal temperature hardening adhesive is charged into the air gap part formed by side leg path parts 34, 34 of right and left leg parts 33, 33 and center path parts 28, 28, and further, joint parts 27 and 37 between a center leg laminated iron core 25 and a side leg laminated iron core 30. The acryl 2-liquid normal temperature hardening adhesive is used instead of a heating curing type adhesive, thereby making it unnecessary to heat a transformer, a heating line and a heat insulating and cooling line are eliminated, and man-hour and personnel are reduced. Further, the displacement in characteristics due to heating is eliminated, and the number of inspection processes before and after heating can be reduced from two to one. A part with no adhesive caused by hanging of the adhesive due to heating is not generated.