The present invention provides a position estimation apparatus capable of determining whether an estimated value deviates from an actual value and trying a process to correct the estimated value if the estimated value is determined to be incorrect. The position estimation apparatus employs a position prediction unit configured to produce a prediction of the position of a mobile object having an odometry sensor mounted thereon, an environment observation unit configured to keep track of each feature point in the environment of the mobile object, a prediction-error check unit configured to determine whether the position prediction produced by the position prediction unit is correct or incorrect, a position-prediction correction unit configured to correct a wrong position prediction and a position/posture updating unit configured to update the position and/or posture of the mobile object on the basis of a correct position prediction.