A method for fabricating a circuit device is provided. An insulation resin sheet having the first conductive layer 3 and the second conductive layer 4 adhered to each other by insulation resin 2 is used, the first conductive path layer 5 is formed by the first conductive layer 3, and semiconductor elements 7 are adhered to and fixed on overcoating resin 8 that covers the first conductive path layer 5, thereby freely routing the first conductive path layer 5 having fine patterns below the semiconductor elements 7. Furthermore, the second conductive layer 4 that has been formed to be thick is removed after a package is sealed with a sealing resin layer 13, and external electrodes 14 are formed in through holes of the insulation resin 2.