A coil unit configured to transmit or receive electric power by electromagnetic induction in a noncontact manner, including: a coil into or from both terminals of which a high-frequency voltage is input or output; a metal conductor placed near the coil; and a first capacitor and a second capacitor connected to the terminals of the coil, wherein the ratio of the capacitance between the first capacitor and the second capacitor is set to a value at which a current induced into the metal conductor due to capacitance coupling when a high-frequency voltage is input into or output from the coil is reduced.