To prevent deterioration of working efficiency of a coil winding, in a single phase transformer which can switch a tap voltage, caused by the work for guiding an intermediate guiding tap wire by automatically and temporarily interrupting the work of continuous winding at a high speed during the coil winding work at the time of guiding the intermediate guiding tap wire.

This single phase transformer is composed of an iron core, a primary coil and a secondary coil wound to the iron core, and can switch a tape voltage. The primary coil or secondary coil is composed of a single coil including an intermediate guiding tap wire and a single coil not including an intermediate guiding tap wire. When an intermediate tap voltage is connected, numbers of turns of both single coils are set to the same number.