Resolver and servo motor

A resolver that detects an angle of rotation of a rotor relative to a stator, wherein

• the stator includes:
• a first exciting coil provided on a sheet-like first board;
• and
• a first transformer coil provided on the first board,
• the rotor includes:
• a first detecting coil provided on a sheet-like second board, facing the first exciting coil in a rotary shaft direction;
• and
• a second transformer coil provided on the second board, connected to the first detecting coil and facing the first transformer coil in the rotary shaft direction,
• the first board is provided with electric elements placed around a rotary shaft and inward of the first transformer coil, and signal wires connecting the electric elements and an external control device,
• the first transformer coil includes:
• a first outer portion that is extended in a circumferential direction of the rotary shaft to form an arc shape;
• and
• a first inner portion that forms an arc shape extended in the circumferential direction and that is provided continuously with the first outer portion around the rotary shaft and inward of the first outer portion, with a first air gap in between,
• the second transformer coil includes:
• a second outer portion that forms a ring shape closed in the circumferential direction;
• and
• a second inner portion that is connected to the second outer portion to form a ring shape closed in the circumferential direction and that is provided around the rotary shaft and inward of the second outer portion, with a second air gap in between,
• the first air gap and the second air gap are provided, facing each other in the rotary shaft direction, and
• the signal wires are routed in an opening region in which the first outer portion and the first inner portion are not present, in a ring-shaped region in which the first transformer coil is extended.