A coil substrate includes a flexible substrate having first and second ends, a first coil formed on first surface of the substrate such that the first coil has center space and first wiring surrounding the space, and an second coil formed on second surface of the substrate such that the second coil has center space and second wiring surrounding the space and is positioned directly below the first coil. Each of the first and second wirings has outer and inner ends such that each wiring is formed in spiral shape between the outer and inner ends, a number of turns in the first coil is greater than a number of turns in the second coil, a width of the first wiring is substantially constant from the outer end to the inner end, and a width of the second wiring is not constant from the outer end to the inner end.