Slope failure is an important disaster that should be taken into consideration, such as slope failure of highway slopes that have a large negative impact on society and slope failure that occurs near residential areas that can cause loss of human life. This study was initiated to investigate the shear properties of a mountain slope composed of volcanic soil at an elevation of about 1,400 m, where a landslide occurred in the past. However, we experienced the difficulty of carrying the undisturbed sample back to the site because of the 2.5 km long uphill and downhill mountain road and the water spewing from the disturbed sample that we brought back. Therefore, a testing machine was fabricated to conduct in-situ tests with less disturbance to the site-specific soil structure.