In order to provide a numerical control method and a device thereof capable of avoiding interference of a tool with a rotary table or a workpiece, without worker's manual operation for performing an interference avoiding operation, there is provided an avoidance-height calculating unit that calculates an interference avoidance height of the tool at which the tool does not interfere with the rotary table and the workpiece over an entire movable range of a rotary shaft to which the movement command is input, an interference determining unit that determines whether the tool will interfere with the rotary table and the workpiece by comparing a current height of a tip of the tool with the interference avoidance height, and an avoiding-operation generating unit that generates a command for movement in a tool shaft direction to the interference avoidance height.