A printed circuit board (PCB) including an impedance-matched strip transmission line includes a strip transmission line including a main line and at least one pair of branch lines branching off from the main line. An upper ground layer is disposed over the strip transmission line and has upper opening parts corresponding in position to the branch lines. A lower ground layer is disposed under the strip transmission line and has lower opening parts corresponding in position to the branch lines. The upper and lower opening parts are symmetric about the branch lines of the strip transmission line.