A phase shifter includes a transformer including a first coil, a second coil that is magnetically coupled to the first coil, and a parasitic inductance component, and an impedance adjustment circuit including a reactance element connected to the transformer. The impedance adjustment circuit includes an input/output capacitor connected between a first port and a second port of the transformer, and the input/output capacitor is defined by an inter-coil capacitance generated between the first coil and the second coil and an input/output additional capacitor connected between the first port and the second port.