A simulation apparatus of a numerical controller that controls a movable unit of a machine tool on the basis of a machining program sequentially generates, when the machining program includes a machining cycle command, a series of movement commands from designated work shape data and machining conditions, and stores the movement commands in a memory. The simulation apparatus displays the machining program and a moving image of the machining program in first and second areas of a display screen and displays the movement commands generated from the machining cycle command in a third area of the display screen.