A waveguide structure includes a signal line and two static lines. The signal line is disposed between the static lines in a first direction. The static lines and the signal line are disposed parallel to one another. Each static line includes a first conductive pattern, a second conductive pattern, and a third conductive pattern. The first conductive pattern and the signal line are disposed on an identical plane of a dielectric layer. A thickness of the first conductive pattern is substantially equal to a thickness of the signal line. The second conductive pattern is disposed on the first conductive pattern. A width of the first conductive pattern is larger than a width of the second conductive pattern in the first direction. The third conductive pattern is disposed on the second conductive pattern. A width of the third conductive pattern is larger than the width of the second conductive pattern.