Crustal stress measurements were carried out monthly by a hydraulic fracturing method at the Rokko-Suwayama test site in Hyogo Prefecture. To determine a three-dimensional stress state, the measurements were made in three boreholes with lengths of about 15m and independent directions. The purpose of the measurements was to obtain basic data (1) to ascertain the reproducibility of a determined stress state and (2) to examine the applicability of the method to detecting a change in a stress state with time. To this end, exactly the same fractures were reopened in each measurement. During reopening them, the secondary-breakdown and the stable-flow pressures were measured. In order to attenuate pulsations of about 2-3 MPa in hydraulic pressure, an accumulator was engaged in the measurements. The accumulator consequently reduced the error of the measurements to about one-tenth compared with that of the previous ones. The stresses thus obtained were discussed in detail. It was ascertained that the method presently improved can detect a change with time of about 0.5 MPa (10%) and a change of 10° in a direction of principal axis.