To shorten the time required to lift a spindle for tool breakage detection in a circuit board driller.

Light projecting and light receiving heads 59 and 60 are arranged between opposing faces of an opening and closing arm 30 arranged below a pressure foot 20, and tool breakage detection is performed at a timing when a lower end of a tool T on a tip of a spindle 11 becomes slightly (1 mm or less) higher than a lower face (pressing face) 36a of a pressing part 36 below the pressure foot 20 after machining. By this, a lifting stroke of the spindle 11 required for a tip of the tool T to move to a height position facing these light projecting and light receiving heads 59 and 60 is reduced for enabling tool breakage detection in a short time after machining.