The Shin-Aimoto Hydro-electric Power Station of 124MW has been completed on Kurobe River by Kansai Electric Power Company in 1985. The construction of the longest headrace tunnel of 5.7km was subject to the critical path in the whole project. The feasibility study was carefully carried out from the rock mechanical point of view. Rocks are gneiss, diorite and limestone which belong to Hida Metamorphic Zone in the central Japan, and the mechanical characteristics of rocks showed remarkable variation with wide range. Rock classification was discussed geostatistically with the combination of CRIEPI's method and Barton's Q-system. In order to get successful result in rapid excavation the TBM and long drill-and-blast methods were applied to the above-mentioned headrace tunnel. Also, the mechanism of “loosening” has been analyzed in comparison between TBM and blasting methods.