Provided is a water reforming effect determination device capable of evaluating water reformation in a short period of time. A water reforming effect determination device is characterized by being provided with a first measurement instrument for using an AC electrode method to measure the capacitance between a pair of electrodes immersed in water supplied to a water reforming device, a second measurement instrument for using the AC electrode method to measure the capacitance between a pair of electrodes immersed in water discharged from the water reforming device, and a calculator for calculating the ratio (Y/X) of the capacitance X for the water that is output by the first measurement instrument when the AC frequency is 100 Hz or less and the capacitance Y for the reformed water that is output by the second measurement instrument when the AC frequency is the same as that for the first measurement instrument.