PURPOSE: To simply and readily stop the fluctuation of the inner body of a transformer by associating two fluctuation stoppers having displaced pin inserting holes and pins.

CONSTITUTION: The assembling torelance of an inner body 1, the welding tolerance of the lower fluctuation stopping pin 8 of the bottom plate of a lower tank 6 and further the manufacturing tolerance of upper and lower tanks 6, 7 are presented as an interval between the engaging hole center O14 of a fluctuation stopping disc 14 and the engaging hole center O15 of the fluctuation stopping disc 15 provided at a fluctuation stopping seat 11. However, the center distance L of the two discs 14, 15 is represented by L=2A sin (θ/2), where the center position of the disc 14 is O14, the position of the pin 9 is O9 and the center position of the disk 15 is O15 and the angle between O14-O9 and O9-O15 is θ. The displacement of the centers of the two discs and the pin or the center of the inserting hole of the pin is set to 1/2 of the maximum displacing size of the inner body to the tank to absorb the dimensional tolerance.