A printed circuit board has a printed wiring board and a semiconductor package mounted on the printed wiring board. The printed wiring board has a signal conductor pattern and a resonance portion resonating with a plurality of resonance frequencies. The resonance portion has a plurality of conductor patterns aligned while separated each other to oppose to the ground conductor pattern through an insulating layer. The plurality of conductor patterns are arranged so as to oppose to the ground conductor pattern which is connected to a ground terminal of the semiconductor package. The resonance portion has a connecting conductor connecting the conductor patterns adjacent to each other. The resonance portion has a via conductor connecting the conductor pattern with the signal conductor pattern. The printed circuit board can reduce an exclusive region of the resonance portion interrupting a plurality of harmonic components, and can reduce EMI originating in a digital signal.