It is extremely important for engineers to select suitable excavation machinery in the early stages of a project in which rock excavation is considered. Therefore, the prediction of bulldozer ripper production from geological data has been carried out. But, in the case of shaft excavation in soil and rock masses, there is no good way to estimate excavatability. In this paper, the authors propose a new method to assess shaft excavatability by the use of EI (Excavatability Index). EI is defined by conventional RQD using drill cores and RQD obtained by observing the corresponding borehole wall. And its validation for engineering applications is demonstrated.