A printed wiring board is provided with a wiring layer, a first ground layer, a second ground layer, a grounding through-hole, a signal through-hole, a first clearance, and a second clearance. The wiring layer has a signal line. The first ground layer has a first ground plane. The second ground layer is positioned between the wiring layer and the first ground layer and has a second ground plane. The grounding through-hole passes through the wiring layer, the first ground layer, and the second ground layer and is connected to the second ground plane. The signal through-hole passes through the wiring layer, the first ground layer, and the second ground layer and is connected to the signal line. The first clearance is formed in the first ground layer, is positioned in the vicinity of the signal through-hole and the grounding through-hole, and separates the first ground plane from the signal through-hole and the grounding through-hole. The second clearance is formed in the second ground layer, is positioned in the vicinity of the signal through-hole, and separates the second ground plane from the signal through-hole.