A gate resistance adjustment device has a waveform input unit that inputs waveforms of a drain voltage or a collector voltage and a drain current or a collector current at least one of during which a switching device is turned on and during which the switching device is turned off, an extraction unit that extracts time required for at least one of turning on or off the switching device and a steady-state drain current or a steady-state collector current of the switching device based on the waveforms input by the waveform input unit, a calculator that calculates a gate resistance of the switching device based on the time and the steady-state drain current or the steady-state collector current that are extracted by the extraction unit, and a setting unit that sets a gate resistance calculated by the calculator in the switching device.