To evaluate the site effects above the engineering base rock with an S-wave velocity of 300m/s, microtremor measurements on the ground surface were conducted in Maizuru, Japan. An estimation method of S-wave amplification spectrum using the microtremor H/V spectral ratio was applied at the ground surface, estimating S-wave amplification spectrum without any ground information based on the microtremor measurement results. It was found that the evaluation of S-wave amplification spectrum needs a revision on the microtremor H/V spectral ratio, using some coefficients on the microtopography classification and the shape of the microtremor H/V spectral ratio.