A stack package includes first and second sub-chip stacks stacked on a package substrate and bonding wires. The first sub-chip stack includes first and second sub-chips. The first sub-chip has a first surface on which a first common pad is disposed. The second sub-chip has a third surface on which a second common pad is disposed. The third surface is bonded to the first surface such that the second common pad is bonded to the first common pad. The second sub-chip includes a fourth surface opposite to the second common pad and a through hole extending from the fourth surface to reveal the second common pad. The bonding wire is connected to the second common pad via the through hole and electrically connects both of the first and second common pads to the package substrate.