1. An activity map creating device that creates an activity situation of a moving object in a monitoring area, and outputs an activity map visualizing the activity situation of the moving object, the device comprising a processor and a memory that stores an instruction, the device further comprising, as a configuration when the processor executes the instruction stored in the memory: a moving object detector that detects the moving object from a captured image of the monitoring area, and that obtains a moving object frame representing an area where the moving object detected from the captured image of the monitoring area is present; a first activity value obtainer that obtains a moving object activity value indicating a degree of activity of the moving object for each of predetermined detection elements plurally divided from the captured image based on detection results of the moving object detector, wherein the first activity value obtainer counts a number of times of presence of each of the detection elements within a setting range based on the moving object frame obtained by the moving object detector to obtain a moving object activity value for each of the detection elements; a target area setter that sets a target area in the monitoring area in accordance with input operation by a user; a second activity value obtainer that aggregates, in the target area, moving object activity values for the respective detection elements obtained by the first activity value obtainer, to obtain a moving object activity value for the target area; a map generator that generates the activity map for the target area based on the moving object activity value of the target area obtained by the second activity value obtainer; and an output information generator that generates output information including a map image that displays the activity map generated by the map generator and overlapped on the captured image of the monitoring area.