TRANSFORMER AND LEAKAGE TRANSFORMER

A transformer 10 comprises a bobbin 20. A cylinder portion 28 of the bobbin 20 is provided with a first winding part 35 where a first wire 37 is wound and a second winding part 36 where a second wire 38 is wound at a position different from the first winding part 35 in an axial direction. At an outer circumference of the cylinder portion 28 located between the first winding part 35 and the second winding part 36, an insulating partition collar 30 is formed. On the first winding part 35, a winding partition collar 33, separating in respective sections S1, S2, is formed. On the winding partition collar 33, at least one communication groove 33a, communicating the sections S1, S2 adjacent to each other is formed. The first wire 37 is a-wound around the first winding part 35.