Coil unit, wireless power transmission device, wireless power receiving device, and wireless power transmission system

A coil unit comprising:

• a magnetic body that includes a first main face and a second main face facing the first main face;
• a first coil made of a first conductor winding spirally around a first axis;
• and
• a second coil made of a second conductor winding spirally around a second axis once or more,
• wherein the first coil has a first coil face intersecting the first axis and is disposed such that the first coil face faces the first main face,
• the second coil has a second coil face intersecting the second axis and is disposed such that the second coil face faces the second main face,
• the first coil face has a first opening,
• the second coil face has a second opening,
• at least a part of an inner edge of the second opening is separated from the magnetic body, and
• the second coil is configured to generate a magnetic field in a direction opposite to a direction of a magnetic field generated by the first coil.