To ensure easy replacement of taps by providing a transformer, having a plurality of taps, a first winding and a second winding, both of which are wound around an iron core, and points of connection or disconnection with taps, and further by providing a separate tap-switching device in addition to the transformer.

The main unit of a transformer 1 has a first winding, second winding, each wound around an iron core, and a plurality of taps. A bushing 5 for switching a plurality of taps is mounted in the transformer 1 is connected with a tap-switching device 3 to be connected or disconnected by a clip 6 with a disconnecting switch. The clip 6 is fixed at the end side of a conductor 14, which is provided in a bushing 13 of the tap-switching device with a mounting member 43. The clip 6 has a spring feature and is fitted with a conductor 44 of the bushing 5 of the main unit of the transformer. The tap-switching device 3 is constituted of a vacuum switch, and has a tap-switching part and an operating device. A counter 10 is mounted on the tap-switching device 3, and the counter 10 displays the number of frequencies of switching. As a result, replacement of tap-switching devices can be made easily, and the main unit of the transformer is not affected even if accidents should occur.