TRANSFORMER

PROBLEM TO BE SOLVED: To provide a transformer whose core can be downsized and in which chipping of an outer pole is prevented even when a core piece swings.SOLUTION: Mutually combined first core 2a and second core 2b, a first coil 11 and a second coil 12 are provided. The first core 2a and the second core 2b include an inner pole 3, an outer pole 4 and a base part 5. At least one of the first core 2a and the second core 2b comprises two or more core pieces 20. An abutting face 40 of the outer pole 4 has a curved portion 42 and a linear portion 41 at a side 43 on the side of the inner pole 3 when viewed from a Z direction. The curved portion 42 is curved along an outer peripheral edge 130 of a large diameter coil 13 which is a coil having a larger diameter between the first coil 11 and the second coil 12. The linear portion 41 is formed linearly.