Abstract: A transmission board includes: an insulating carrier; a pair of differential channels, including a first channel and a second channel; and a grounding structure, provided in the insulating carrier. An inner side of the first channel and an inner side of the second channel are separated from and coupled to each other. The first channel has a timing compensation section and a connecting section connected to the timing compensation section. A distance between an inner side of the timing compensation section and the inner side of the second channel is defined as a first distance. A distance between an inner side of the connecting section and the inner side of the second channel is defined as a second distance. The first distance is greater than the second distance. The grounding structure is located between the inner side of the timing compensation section and the inner side of the second channel.