A multilayer circuit substrate includes: a first signal line and a first ground conductor formed in a first conductive layer; and a second signal line and a second ground conductor formed in a second conductive layer, the second conductive layer facing the first conductive layer across an insulating layer. The first signal line intersects with the second signal line in a plan view of the multilayer circuit substrate, a space between the first ground conductor and first signal line is smaller in an intersection area of the first and second signal lines than a space in a non-intersection area, a space between the second ground conductor and second signal line is smaller in the intersection area than a space in the non-intersection area, and the first signal line is formed at a smaller line width in the intersection area than in the non-intersection area.