An instrument for measuring the characteristics of a tuner comprising means (1, 2) for sweeping the frequency (Fs) of an RF signal from the initial frequency (Fs1) to the final frequency (Fsn) and delivering the RF signal being swept to the tuner, a means (3) for detecting the voltage of a signal having an intermediate frequency, a means (4) for detecting a logarithmic voltage obtained by subjecting the voltage of a signal having an intermediate frequency to logarithmical conversion, a means (5) for detecting a voltage indicative of voltage standing wave ratio, and means (6, 7, 81, 82, 83, 1) for taking in the voltage of a signal having an intermediate frequency, the logarithmic voltage obtained by subjecting the voltage of a signal having an intermediate frequency to logarithmical conversion, and the voltage indicative of voltage standing wave ratio during a first period when the frequency (Fs) of the RF signal is swept from the initial frequency (Fs1) to the final frequency (Fsn).