A phase mixer includes a phase mixing unit configured to mix a phase of a first input signal and a phase of a second input signal in response to a phase control signal and output a phase mixed signal whose phase is varied by one or more units of a unit phase value, and a phase value adjusting unit configured to control an operation of the phrase mixing unit so that the unit phase value is adjusted in response to a code signal coding at least one of a process, voltage, or temperature (PVT) variation.