A transformer includes: a rotary shaft configured to rotate about a central axis of the rotary shaft as a rotational axis; a primary-side first coil configured to extend around a first axis perpendicular to the central axis; a secondary-side second coil configured to extend around a second axis and supported by the rotary shaft, the second axis being perpendicular to the rotational axis in an area surrounded by the first coil; and a secondary-side third coil configured to extend around a third axis and supported by the rotary shaft, the third axis being perpendicular to the rotational axis and forming a predetermined angle with the second axis in the area.