Preceding the eastern Yamanashi earthquake of magnitude 6.0, an anomalous tilt change up to 0.4 micro-radian was detected by the borehole-type tiltmeter at the Enzan station locating 31km north-west of the epicenter. The anomaly began 18 days preceding the earthquake and continued 10 days. The tiltmeter was installed at the bottom of the well of 89m depth. The resolution is 0.006μ radian and the long-term stability is better than a few μ radian per year. This tiltmeter had recorded similar tilt changes of the order of 0.4μ radian twice since it was installed in 1979. Both the changes had been caused by a large amount of precipitation accompanied by typhoons. During these 10 days, however, the maximum daily precipitation was 20mm, temperature change was smaller than 0.05°C at the bottom of the well, and there was no construction near the station. Therefore, we may interpret this anomalous tilt change as a precursor of the earthquake. The station is located in the fracture zone associated with the active fault, the Daibosatsurei-nishigawa fault; core samples obtained from the well were fractured and their P wave velocity was extremely low. The direction of the anomalous tilt vector change is nearly orthogonal to the strike of this active fault. This suggests that the observed upheaval of the epicentral block is the consequence of the hinge movement at the fault.