A monitoring device for performing monitoring of operations of an actual machine, the device comprising: an acquisition unit adapted to acquire actual operation data that indicates actual operations of each portion of an actual machine from a control device which controls the actual machine; a display item setting unit adapted to set display items that are included in a timing chart that is displayed on a display device; and a storage unit, wherein the storage unit is adapted to store reference operation data indicating a reference operation of each portion of the actual machine, first related information that associates specific actual operation data and reference operation data with the display items, and second related information that associates components that are included in a virtual machine on an image that simulates the actual machine with the specific actual operation data and the reference operation data, the monitoring device being characterized in further comprising: a timing chart generation unit adapted to generate, for the display items, an actual operation timing chart that indicates a temporal change in an actual operation on a basis of actual operation data corresponding to the display items in the first related information and a reference operation timing chart that indicates temporal change in a reference operation on a basis of reference operation data corresponding to the display item in the first related information, and displays the actual operation timing chart and the reference operation timing chart on the display device; and a simulation data generation unit adapted to generate simulation data of a reference image that is an image when the virtual machine performs a reference operation and a real image that is an image when the virtual machine performs an actual operation, on a basis of the reference operation data and the actual operation data that are associated with the components in the second related information. an acquisition unit adapted to acquire actual operation data that indicates actual operations of each portion of an actual machine from a control device which controls the actual machine; a display item setting unit adapted to set display items that are included in a timing chart that is displayed on a display device; and a storage unit, wherein the storage unit is adapted to store reference operation data indicating a reference operation of each portion of the actual machine, first related information that associates specific actual operation data and reference operation data with the display items, and second related information that associates components that are included in a virtual machine on an image that simulates the actual machine with the specific actual operation data and the reference operation data, the monitoring device being characterized in further comprising: a timing chart generation unit adapted to generate, for the display items, an actual operation timing chart that indicates a temporal change in an actual operation on a basis of actual operation data corresponding to the display items in the first related information and a reference operation timing chart that indicates temporal change in a reference operation on a basis of reference operation data corresponding to the display item in the first related information, and displays the actual operation timing chart and the reference operation timing chart on the display device; and a simulation data generation unit adapted to generate simulation data of a reference image that is an image when the virtual machine performs a reference operation and a real image that is an image when the virtual machine performs an actual operation, on a basis of the reference operation data and the actual operation data that are associated with the components in the second related information. a timing chart generation unit adapted to generate, for the display items, an actual operation timing chart that indicates a temporal change in an actual operation on a basis of actual operation data corresponding to the display items in the first related information and a reference operation timing chart that indicates temporal change in a reference operation on a basis of reference operation data corresponding to the display item in the first related information, and displays the actual operation timing chart and the reference operation timing chart on the display device; and a simulation data generation unit adapted to generate simulation data of a reference image that is an image when the virtual machine performs a reference operation and a real image that is an image when the virtual machine performs an actual operation, on a basis of the reference operation data and the actual operation data that are associated with the components in the second related information.