PURPOSE: To provide an arc furnace transformer where a tap selector is not required to be frequently replaced by a method wherein two or more fixed contact points connected to the same tap lead are provided.

CONSTITUTION: Fixed contact points 7 are provided to the outer surface of the cylindrical case of a tap selector 6. An upper movable part M1 and a lower movable part M2 are provided to the upper part and lower part of the tap selector 6 inside the case in such a manner that the movable parts M1 and M2 are moved by a drive source. A movable contact point 8 capable of coming into contact with or being detached from one of the fixed contact points 7 with its movement is provided to each of the movable parts M1 and M2. The fixed contact points 7 are divided into two groups which are separately covered by the movable parts M1 and M2. Tap leads 5 of taps T1, T6 to T9 are led out from a tap winding 4. The tap leads 5 of the T6 to T9 which are very often used are connected to the two fixed contact points 7. The two fixed contact points are selected out of an upper fixed contact point group and a lower fixed contact point group respectively.