To provide an oil-immersed transformer in which a tank is improved in corrosive resistance since the oil-immersed transformer has a problem of oil leakage due to corrosion of the tank etc.

The tank and an upper lid of the transformer are made of ferrite-based stainless steel, and contain one or more kinds among 7.0 to 14.0% by mass of Cr and 0.08 to 2% of Ti, 0.08 to 2% of Nb, 0.01 to 1% of Al, 0.08 to 2% of Ni, 0.08 to 2% of Cu, 0.08 to 2% of Mo, and 0.08 to 2% of W to be improved in corrosion resistance. Further, components of the material are suitably selected not to impair processability of manufacture.