A bonding structure of a sheet core and a pair of flange parts wherein the pair of flange parts is formed on both ends of a shaft part to constitute a drum core together with the shaft part; the sheet core is bonded, in a manner connecting the pair of flange parts across the shaft part, to the top faces of the flange parts facing away from the bottom faces of the flange parts to be mounted on a circuit board; and a coil-shaped conductor is constituted by sheathed conductive wires wound around the shaft part; wherein the bonding surfaces of each of the flange parts and the sheet core have multiple contact areas where the flange part makes direct contact with the sheet core, as well as adhesive areas between the contact areas where an adhesive is disposed.