The pressure test and the wind tunnel test were carried out to obtain basic data for wind resistance design method of a mechanically anchored waterproofing membrane system. The test specimen was a flat roof with dimensions; 2.4m-wide, 3m-length and 0.29m-height. The waterproofing material was polyester fiber-reinforced PVC sheet. In pressure test, because the applied pressure is equivalent pressure on all area of the roof, the billowing height of PVC sheet around fastener were almost same values. Therefore, the vertical force at fastener was also same with the pressure induced by a compressor and horizontal force was approximately 0N. On the other hand, the strain of PVC sheet around fastener at windward was larger than that of leeward in the wind tunnel test. Then, the horizontal force was 70% of vertical force at mean wind speed of 38.6 m/s. Therefore, it was clear that characteristic of mechanically anchored waterproofing membrane system in pressure test and wind tunnel test was different.