Provided is a phase shifting device including a first balun outputting first and second differential input signals, an I/Q generator outputting first to fourth phase signals based on the first and second differential input signals, a control circuit outputting a first control signal, a second control signal, a plurality of in-phase select signals, and a plurality of quadrature select signals, a current source circuit including a first source transistor outputting an in-phase current according to the first control signal and a second source outputting a quadrature current according to the second control signal, a vector sum circuit outputting first and second differential output signals based on the first to fourth phase signals according to the plurality of in-phase select signals and the plurality of quadrature select signals and including a plurality of sub-vector sum circuits, and a second balun outputting an output signal.