A monitoring system having a monitoring device configured to monitor movement of a worker and a robot to allow the worker to work safely in a work area (α) in which the worker and the robot work, the monitoring system comprising: a detection part configured to detect a position of the worker that has intruded into the work area (α); a first specifying part configured to specify a worker movable area indicating a range in which the worker is movable in a predetermined period of time on the basis of the position of the worker detected by the detection part and a presumed movement speed of the worker; an image capturing part configured to capture an image of an area including at least the worker movable area specified by the first specifying part and a predetermined robot occupied area of the robot through which it is predicted that the robot will pass on the basis of the current movements of the robot; a second specifying part configured to specify a robot movable area indicating a range in which a movable portion of the robot is movable according to the image of the area captured by the image capturing part; a third specifying part configured to specify a human body area of the worker by a range of three-dimensional coordinates according to the image of the area captured by the image capturing part; a measuring part configured to measure a distance between the robot movable area specified by the second specifying part and a cluster information item of the human body area specified by the third specifying part which is closest to the robot movable area; and a restricting part configured to restrict movement of the robot when the distance measured by the measuring part is equal to or less than a predetermined distance (Lc). a detection part configured to detect a position of the worker that has intruded into the work area (α); a first specifying part configured to specify a worker movable area indicating a range in which the worker is movable in a predetermined period of time on the basis of the position of the worker detected by the detection part and a presumed movement speed of the worker; an image capturing part configured to capture an image of an area including at least the worker movable area specified by the first specifying part and a predetermined robot occupied area of the robot through which it is predicted that the robot will pass on the basis of the current movements of the robot; a second specifying part configured to specify a robot movable area indicating a range in which a movable portion of the robot is movable according to the image of the area captured by the image capturing part; a third specifying part configured to specify a human body area of the worker by a range of three-dimensional coordinates according to the image of the area captured by the image capturing part; a measuring part configured to measure a distance between the robot movable area specified by the second specifying part and a cluster information item of the human body area specified by the third specifying part which is closest to the robot movable area; and a restricting part configured to restrict movement of the robot when the distance measured by the measuring part is equal to or less than a predetermined distance (Lc).