To provide a monitoring device capable of easily detecting the minute movement of a monitoring object with high reliability.SOLUTION: A monitoring device includes a distance measuring device 1 measuring a distance to a measuring point of a monitoring object Pa, and an outside monitor device 10 detecting the occurrence of prescribed movement of the monitoring object Pa on the basis of a measured value of a distance. The measuring point of the distance measuring device 1 is a measuring point which is set so that the measured value of a distance is changed to a value larger than an actual distance by a specified amount or more in accordance with the movement of the monitoring object Pa, or the amount of change of the measured value of a distance becomes larger than the amount of change of an actual distance by a specified amount or more in accordance with the movement of the monitoring object Pa.SELECTED DRAWING: Figure 1【課題】監視対象物の微小な動きを高い信頼性で容易に検知することができる監視装置を提供する。【解決手段】監視装置は、監視対象物Ｐａの測定点までの距離を計測する測距装置１と、距離の計測値に基づいて監視対象物Ｐａの所定の動きの発生を検知する外部モニタ装置１０とを有する。測距装置１の測定点は、距離の計測値が、監視対象物Ｐａの動きに応じて、実際の距離よりも所定量以上、大きな値にまで変化するか、又は、距離の計測値の変化量が、監視対象物Ｐａの動きに応じた実際の距離の変化量よりも所定量以上、大きな変化量になるように設定された測定点である。【選択図】図１
