This invention relates to a method and apparatus for power factor adjustment in a waveguide circuit or a transmission line circuit. In this invention, it is shown that, in a waveguide circuit or a transmission line circuit, the power supplied by the source and the impedance can be adjusted by controlling the amount of the phase change of the signal when it propagates through the (equivalent) transmission line once the medium, the structure, and the load of the waveguide circuit or the transmission line circuit are chosen. It is also shown that, by choosing an appropriate frequency, transmission line, and load, one can achieve the negative power factor of the (equivalent) transmission line circuit, and also make the power delivered from the source be lesser than that consumed at the load.