In such transformers as oil-filled transformers, if the transformer is placed within a ship or a floating wind power tower, there is a possibility that displacement may occur to a coil or core within a tank of the transformer if swinging or tilting continue to be added to the transformer by effects of waves or the like. The present invention provides a transformer which can withstand the effects of such waves. The present invention is a transformer provided with cores, coils wound around the cores, an upper core fastener and a lower core fastener which fix the cores from respective top and bottom directions, and a tank which houses the same, wherein: on the upper core fastener are disposed anti-vibration metal fittings for a core coil assembly incorporating the cores and the coils; the anti-vibration metal fittings have notches; and projections of shapes mating at the notches of the anti-vibration metal fittings are disposed on the inner side of the tank.