A phase shifter includes a first substrate; a microstrip formed on the first substrate so as to extend in a first direction; a ground layer disposed with a space on the upper surface of the microstrip and having a defected ground structure (DGS) with a defected pattern formed therein; a second substrate disposed on the ground layer; and a liquid crystal layer disposed in a space between the first substrate and the second substrate, wherein DC voltage is applied between the ground layer and the microstrip.