A phase shifter fabricated by a simple process and having a simple structure, a method of fabricating the same, and a duplexer having the same are disclosed. The duplexer includes a transmitting-end filter capable of passing only a signal in the range of a transmission frequency, a receiving-end filter capable of passing only a signal in the range of a reception frequency, and a phase shifter interposed between the transmitting-end filter and the receiving-end filter to isolate a transmitted signal of the transmitting-end filter and a received signal of the receiving-end filter from each other. The phase shifter includes a substrate provided with an input port and an output port, an inductor formed on the substrate and connected to the input and output ports, and a capacitor provided on the substrate, wherein the capacitor and inductor share a region of the substrate.