The present invention relates to a thin-film device including a thin-film element and a lead conductor film. The thin-film element and the lead conductor film are embedded in an insulating film. The lead conductor film has a terminal area at one end thereof, is connected to the thin-film element at the other end thereof, and between the one end and the other end, has an increased surface area portion whose volume is partially occupied by an insulating material to increase surface area. As a result, there is provided a high frequency thin-film device capable of reducing loss and heat generation due to skin effect, particularly a thin-film magnetic head.