An interface for transmitting a high-speed signal and an optical module including the same. The interface may include a main substrate and a sub-substrate. The main substrate may have at least one high-speed signal line formed on the upper surface of the main substrate. The sub-substrate may have a first conductive line formed on the lower surface thereof so as to adjust high-speed signal transmission characteristics of the high-speed signal line, wherein the first conductive line may be coupled to the upper surface of the main substrate and partially overlap with the high-speed signal line.