A tool radius adjusting device executes an operation for adjusting the tool radius of a boring holder in parallel with execution of a machining program for executing an operation of a spindle head and an operation of a tool changer. A carrier control unit determines whether the tool changer is executing a tool changing process. When the tool changing process is not being executed, the carrier control unit allows the carrier device to execute an operation for picking the boring holder out from the tool magazine and an operation for returning the boring holder, of which the tool radius has been adjusted, to the tool magazine.