A surface property evaluation method includes a measurement step for acquiring the distribution of impedance in the depth direction of a test piece, and an evaluation step for evaluating the surface treatment state in the depth direction and wherein the evaluation step includes: a step for creating a reference measurement value group by preparing untreated sample, good sample, and sample to be evaluated, and calculating an impedance ratio γ1 at each frequency for the untreated sample and good sample impedances; a step for creating an evaluation measurement value group by calculating an impedance ratio γ2 for the impedances of untreated sample at each frequency relative to the sample to be evaluated impedances; and a step for evaluating the surface treatment state of a sample to be evaluated by comparing a reference measurement value group with the evaluation measurement value group.