An objective of the present invention is to provide a printed board being capable of suppressing EMI emissions from power supply wirings. To accomplish the objective, a printed board of the present invention includes a plurality of ground layers disposed in a printed board, a power supply layer put between the plurality of the ground layers, and through holes disposed along at least periphery of the printed board and connecting the plurality of the ground layers, wherein the through holes are disposed at intervals according to a wavelength corresponding to a maximum frequency of electromagnetic waves to be suppressed.Further, a printed board of the present invention includes a power supply layer disposed in a printed board and put between ground layers above and below the power supply layers, and a plurality of through holes connecting the ground layers above and below the power supply layers, wherein the plurality of the through holes are disposed at and near the power supply layer and are spaced apart at intervals according to a wavelength corresponding to a maximum frequency of electromagnetic waves to be suppressed.