A multilayer printed wiring board including insulating layers, conductor layers stacked alternately over the insulating layers, respectively, and viaholes formed in the insulation layers and electrically connecting the conductor layers through the insulation layers. The viaholes include a first group of viaholes and a second group of viaholes. The viaholes in the first group are tapered toward the viaholes in the second group, and the viaholes in the second group are tapered toward the viaholes in the first group. The viaholes in the first group and the the viaholes in the second group are formed in the insulating layers, respectively, and the viaholes are formed by plating openings formed after lamination of respective ones of the insulating layers, and each of the insulating layers is about 100 μm or less in thickness.