A transmission line includes a dielectric base body including a first and second base bodies. Each of the first and second base bodies includes dielectric layers stacked on top of one another. The first base body includes a first signal conductor located between ground conductors in a stacking direction. The second base body includes a second signal conductor located between ground conductors in the stacking direction. The first and second base bodies are brought together so that one of the ground conductors of the first base body and one of the ground conductors of the second base body abut against or are adjacent to each other. Lead conductors defining both ends of the first signal conductor and lead conductors defining both ends of the second signal conductor are exposed on a mounting surface of the dielectric base body parallel or substantially parallel to the stacking direction.