A vibration-suppressed transformer is fixed to a base plate and includes a magnetic lower core, two or more magnetic upper cores, primary and secondary coils. The lower core is on the base plate. The upper cores are arranged face to face over the lower core. The coils are arranged between the lower and upper cores. Each upper core contacts the lower core, on an outer side of the coils, with a first gap being provided between the upper and lower cores, on an inner side of the coils. The upper cores are extended towards each other from the outer to the inner side of the coils, with a second gap being provided therebetween. The second gap is provided therein with a non-magnetic pressing member to press the lower core against the base plate, on an inner side of the coils.