Contactless power supply coil unit

A contactless power supply coil unit comprising:

• a plurality of coils that are wound around a predetermined center axis;
• and
• a holder that holds the plurality of coils;
• wherein the coils are spirally wound in plan view;
• the plurality of coils are disposed so as to overlap in an axial direction and respectively define layers stacked in the axial direction;
• the coils defining adjacent layers are connected in series to each other;
• the holder includes a core extending in the axial direction;
• the core includes a plurality of winding portions disposed along the axial direction;
• the plurality of the coils are respectively wound around the plurality of winding portions;
• and
• outer diameters of the plurality of winding portions each change monotonically along the axial direction.