To provide a leakage transformer that can prevent malfunction due to the shielding of leakage flux, a power-supply unit, and a lighting fixture.

In this leakage transformer where first and second coils 2 and 3 are wound mutually with intervals, and the leakage flux path is formed with the interval, a ferromagnetic body 4 is arranged near the first and second coils 2 and 3.