A primary coil is configured by series connection of a first coil element (L1a), a second coil element (L1b) and a fifth coil element (L1c), and a secondary coil is configured by series connection of a third coil element (L2a), a fourth coil element (L2b) and a sixth coil element (L2c). The coil elements (L1a, L2b, L1c) are disposed coaxially and the coil elements (L2a, L1b, L2c) are also disposed coaxially. The respective coil elements (L1a, L1b, L1c) of the primary coil and the respective coil elements (L2a, L2b, L2c) of the secondary coil are disposed adjacently in a layer direction of a base material layer, respectively. The coil elements (L1a, L1b, L1c, L2a, L2b, L2c) are connected in such a manner that a magnetic field in the same direction is generated in all of the coil elements (L1a, L1b, L1c, L2a, L2b, L2c) when common mode current flows.