A multilayer coil array includes an element body; first and second built-in coils; and first to fourth outer electrodes provided on the element body. A non-magnetic layer is provided between the first and second coils. An end of the first coil extending from the coil conductor closest to the second coil among the plurality of coil conductors of the first coil is connected to the first outer electrode and another end of the first coil is connected to the second outer electrode. An end of the second coil extending from the coil conductor closest to the first coil among the plurality of coil conductors of the second coil is connected to the third outer electrode and another end portion of the second coil is connected to the fourth outer electrode. The second and fourth outer electrodes are connected to output terminals of a switching element of a DC-DC converter.