This paper presents physical and mechanical properties of volcanic ash soils in Hokkaido. A series of test results showed that physical property of volcanic ash soils was strongly influenced by intra-particle void and minerals of soil particles. It was also found that unique relationships between N and φ values existed on volcanic soil grounds. Liquefaction of volcanic soil grounds induced by recent big earthquakes around Hokkaido has been also introduced. According to laboratory test results, it was apparent that liquefaction resistance of pumice flow deposits (D_<rc>=70%) with non-plastic fines was significantly lower than that of dense Toyoura sand.