An information processing device for calculating a current movement amount of a moving object, the device comprising: an internal sensor configured to monitor information including acceleration of the moving object; a first derivation unit configured to derive a first movement amount of the moving object from the monitor information; a second derivation unit configured to derive a second movement amount of the moving object using surrounding information of the moving object monitored by an external sensor; a reliability calculation unit configured to calculate reliability of the second movement amount; and a movement amount calculation unit configured to calculate a current movement amount of the moving object using the first movement amount and the second movement amount when the reliability meets a specific criterion, and to calculate the first movement amount as the current movement amount when the reliability does not meet the specific criterion, wherein the surrounding information is at least one of a photographic image and distance information of a periphery of the moving object, and the reliability calculation unit calculates, as the reliability, the number of errors satisfying a specific condition out of a plurality of errors, each of the errors being an error between an object point, which is used for deriving the second movement amount, in the surrounding information monitored at first timing and an estimation point that is an estimated object point at the first timing using the surrounding information monitored at second timing, characterized in that the specific condition is that a difference in a feature amount between the object point and the corresponding estimation point is equal to or less than a reference value, and the feature amount is a value for each of the object point and the estimation point that is defined in accordance with an edge and a corner. an internal sensor configured to monitor information including acceleration of the moving object; a first derivation unit configured to derive a first movement amount of the moving object from the monitor information; a second derivation unit configured to derive a second movement amount of the moving object using surrounding information of the moving object monitored by an external sensor; a reliability calculation unit configured to calculate reliability of the second movement amount; and a movement amount calculation unit configured to calculate a current movement amount of the moving object using the first movement amount and the second movement amount when the reliability meets a specific criterion, and to calculate the first movement amount as the current movement amount when the reliability does not meet the specific criterion, wherein the surrounding information is at least one of a photographic image and distance information of a periphery of the moving object, and the reliability calculation unit calculates, as the reliability, the number of errors satisfying a specific condition out of a plurality of errors, each of the errors being an error between an object point, which is used for deriving the second movement amount, in the surrounding information monitored at first timing and an estimation point that is an estimated object point at the first timing using the surrounding information monitored at second timing, characterized in that the specific condition is that a difference in a feature amount between the object point and the corresponding estimation point is equal to or less than a reference value, and the feature amount is a value for each of the object point and the estimation point that is defined in accordance with an edge and a corner.