A quality assurance apparatus for a cancer treatment system with an electric field, comprising: an electric field generator configured to transmit an electric field to an inside of an electromagnetic phantom through an electrode array attached to the electromagnetic phantom; a measurement unit configured to measure any one of a voltage, a current, and an electric field inside the electromagnetic phantom; a data collection unit configured to collect a value measured by the measurement unit and convert the measured value into a digital value; an analysis unit configured to calculate and monitor a distribution and intensity of the electric field inside the electromagnetic phantom through the value transmitted from the data collection unit; and a verification unit configured to verify the electric field monitored by the analysis unit.