An apparatus for testing the performance of a synthetic aperture radar is provided. The apparatus for testing the performance of a synthetic aperture radar includes: a three-axis motion platform that is coupled to an antenna and driven in roll, pitch, and yaw directions so as to reproduce motion components generated from a pointing plane of the antenna; a target simulator configured to reproduce a ground target; and a system simulator that allows the three-axis motion platform and the target simulator to work in conjunction with each other in real time, and controls the three-axis motion platform and the target simulator. Here, the three-axis motion platform may include a three-axis driver that determines the attitude of the three-axis motion platform, based on position and speed information received from the system simulator. The target simulator may include a target modulator that adjusts the amplitude of an output signal, performs range and phase delays, and reproduces a Doppler component, based on simulation target information received from the system simulator.