The present invention enables, through an inkjet scheme, unencumbered formation of an electroconductive film on an inner peripheral surface (inner wall) of a hole penetrating from a front surface to a reverse surface of an insulating substrate.　When, on an insulating substrate 11 having a hole 13 penetrating from a front surface to a reverse surface thereof, an electroconductive underlayer is to be formed on at least an inner wall of the hole 13, the following steps are carried out: a filling step for filling the hole 13 with an ink 15 by ejecting electroconductive ink droplets into the hole 13 by inkjet scheme in a state where the hole 13 is blocked up with an enclosing member 17 from the underside of the substrate 11; a discharge step for discharging the ink with which the hole 13 has been filled to the exterior; and a drying step for drying at least an inner wall ink layer remaining on the inner wall of the hole 13 after the discharge step.