A vector sum circuit and a phase controller including the vector sum circuit are provided. The vector sum circuit includes an amplifier configured to amplify an input orthogonal signal by using a first metal oxide semiconductor field effect transistor (MOSFET), and a self body-biasing circuit comprising a resistor. The self body-biasing circuit is configured to connect a drain and a body of the first MOSFET to reduce a voltage connected to the body as a current at the drain increases.