The control section can determine, on the basis of a detection signal from a detection device, whether operation of an element corresponding to the detection device has completed. The display device can display step sequence data and a three-dimensional model of a machine tool operated through simulation. When the abnormality detection section detects an abnormality of the machine tool, the control section extracts, from a ladder circuit corresponding to a step in which an abnormality has been detected, an element to be operated in response to completion of operation of a preceding element in the ladder circuit, or an element not having completed its operation. The control section then specifies a detection device corresponding to the extracted element or a moving part corresponding to the detection device, and displays the element or the moving part in the displayed three-dimensional model in a distinguishable manner.