Printed circuit board in which deterioration of signal transmission characteristics otherwise caused by a stub parasitically formed in a through-hole is suppressed to provide optimum high-speed signal transmission characteristics. A printed circuit board 10 includes a power supply/ground layer 11 and a signal line 12b in a dielectric layer 13, and a through-hole 12 connected to the signal line 12b. A clearance 14 which becomes an anti-pad is provided in an area between the through-hole 12 and the power supply/ground layer 11. The signal line 12b is extended from the through-hole 12 through the clearance 14 to an area below the power supply/ground layer 11. The portion of the signal line 12b arranged in the vicinity of the power supply/ground layer 11 in the clearance 14 has an area of impedance gradient 17 whose characteristic impedance becomes progressively lower in a direction away from the through-hole 12.