PROBLEM TO BE SOLVED: To determine a correct displacement by integrating acceleration measurement value twice without requiring an immovable point, and to enable highly accurate displacement monitoring of the ground, an artificial structure or the like. SOLUTION: In this method, an acceleration sensor is installed in the ground or the like, and the displacement of the ground or the like at a measuring point is calculated and monitored by integrating the measurement value twice. The method comprises a first step of performing one integration by using a trend component calculated by a Kalman filter as a correction value and removing it when the acceleration measurement value is integrated and of converting the acceleration record into speed record, and a second step of converting the speed record to displacement record by calculating the trend component by the Kalman filter again for the calculated speed record, removing it, and performing integration again. COPYRIGHT: (C)2006,JPO&NCIPI