We have proposed here a new structure of printed circuit transmission lines in which the dominant mode leaks power through additional dielectric multilayer without affecting neighboring circuits. Such a structure of a microstrip line has a slot on the ground plane and also has a dielectric multilayer under it. Then the appropriate combination of dielectric constant between dielectric layers produces the leakage into the multilayer. This means that the leaky field does not leak into the substrate of the microstrip line, and then we can get the lossy uniform microstrip line above the critical frequency. We present first the dependence of the structural parameters of the proposed microstrip lines on the leakage properties. We also apply such a structure to slot lines as one of coplanar printed circuit transmission lines and confirm that the leakage effect can be successfully controlled by an additional dielectric multilayer. Finally, we present the experimental results for the microstrip line with the dielectric multilayer to verify the validity of the numerical results.