When a spindle unit 1 rises to a tool change position P1 of a printed-circuit board drilling apparatus, a pair of cam followers 27, which have been spaced downward from a pair of operating pins 38, are brought into engagement with conical portions 39 of the operating pins 38 and caused to move toward each other. As a result, a pair of opening/closing arms 24 that are provided under a pressure foot 20 and that serve as suppressing members for preventing floating of the printed-circuit board are moved away from their suppressing positions A in which the opening/closing arms 24 are kept closed by the force of a spring 28, to their retracted positions B. Consequently, forward end portions of the opening/closing arms 24 are positioned outside a tool passage zone S through which a tool post passes when a tool is changed. As a result, the suppressing members 24 used to prevent floating of the printed-circuit board are retracted without using a drive source, when tool change is made, so that the suppressing members do not become an obstacle to performing the tool change operation.