To provide an oil-immersed transformer which is reduced in floor area, produces less noises, and is suitable for a deck-type substation.

An immersed transformer is equipped with an immersed transformer main body 2 arranged on a floor below a deck 3, and a cooling unit 4 which is arranged on a floor above the deck 3 to cool down the immersed transformer main body 2 by dissipating heat released from the transformer main body 2.