An apparatus for measuring radio frequency output for a magnetic resonance imaging apparatus includes a directional coupler, a signal controller and a converter. The directional coupler is variable in degree of coupling, and configured to attenuate a radio frequency signal which is generated in a radio frequency signal generator and amplified in a radio frequency power amplifier. The signal controller is configured to control the degree of coupling of the directional coupler. The converter is configured to perform a digital conversion of the radio frequency signal from the directional coupler so as to output a digital signal.