PURPOSE: To safely and reasonably conduct the earth retaining work.

CONSTITUTION: The first processing means 42 performs the repetitive extended Kalman filter process based on the measured data including the displacement of a wall body and the axial force of a strut and the prescribed assumed value including the back face side pressure of a wall to be estimated and the initial value of the ground reaction coefficient. A weighting means 44 weights the error covariance value of the obtained estimated value. The second processing means 45 performs the repetitive extended Kalman filter process based on the estimated value obtained by the first processing means 42 and the weighted covariance value as the initial values. A convergence judging means 46 judges the convergence of the estimated value to obtain the optimum estimated value. A prediction analysis section 6 predicts the deformation and stress state of an earth retaining frame based on the optimum estimated value or the like.