A packaging method, a packaging structure and a package is substrate capable of restraining a warp of a thin film substrate, increasing a product yield, and building up a sufficient cooling capacity in the case of mounting an LSI having a high exothermic quantity. A package substrate 1 of the invention is such that an opening 11 is formed in a first substrate 12, a thin film substrate (a second substrate) 13 is laminated on the first substrate 12, the opening 11 is covered with the thin film substrate 13. Next, a capacitor (a first electronic part) 14 is inserted into the opening 11 and bonded to the thin film substrate, a resin 15 fills an interior of the opening 11 to a fixed or larger thickness and is hardened, the thin film substrate 13 and the capacitor 14 are thereby sustained by the resin 15, an LSI 16 (a second electronic part) that should be connected to the capacitor 14 is bonded to a surface, on an exposed side, of the thin film substrate 13, and the capacitor 14 is connected to the LSI 16.