To suppress occurrence of a difference in transmission time due to a difference in length between signal lines, there is provided a printed wiring board having: an insulating substrate (10); a first signal line (L31) formed on the insulating substrate (10); a second signal line (L32) having a shorter length than that of the first signal line (L31); and a ground layer (30) formed for the first signal line (L31) and the second signal line (L31) via an insulating material (10). The ground layer (30) includes a first ground layer (G31) corresponding to a first region (D1) and a second ground layer (G32) corresponding to a second region (D2). The first region (D1) is defined based on the first signal line (L31) and has a first predetermined width (W31). The second region (D2) is defined based on the second signal line (L32) and has a second predetermined width (W32). The first ground layer (G31) has a remaining ratio lower than a remaining ratio of the second ground layer (G32).