A preceding-check processing sequence is provided separately from a machine-control processing sequence for an actual machine control, to make it possible to perform a collision check at an accurate position from an operation restart time of a machining program even when an operator interrupts an operation in the middle of the machining program or when the operator interrupts the operation as having detected a collision. This preceding-check processing sequence performs a collision possibility check ahead of an actual machine control. In this arrangement, there is provided a control-state synchronizing unit that matches a state of the preceding-check processing sequence with a state of the machine-control processing sequence during a period from when a machine stops until when the machine restarts an operation.