A PCB includes a PCB body at least including a first metal layer, a second metal layer, and a first ground layer sandwiched therebetween; and a pair of transmission lines including a first transmission line conductor and a second transmission line conductor. The first transmission line conductor is located in the first metal layer which has two straight line sections at its two ends and a curved line section at its middle, the second transmission line conductor has two straight line sections at its two ends which are located in the first metal layer and a cross-via structure at the middle which has a buried trace buried in the second metal layer, and the curved line section and the buried trace are isolated by the first ground layer. Skew effect of the differential transmission circuit is reduced, thereby improving the signal transmission quality and improve signal transmission speed.