PURPOSE: To provide a device for fixing respective ends of parallel longitudinal bridges to cross bridges by self tapping screws automatically.

CONSTITUTION: A cross bridge A is mounted on n outside table 1 and a longitudinal bridge B parallel to it is mounted on an inside table 3 respectively. A screw-in device 19 of a supply tapping screw C is mounted on a traveling member 6 for traveling along the cross bridge A intermittently outside the outside table 1. A pressure device 28 of the cross bridge A and the longitudinal bridge B and a clamp device 31 of a fixed longitudinal bridge are mounted and the tapping screw C is screwed in the longitudinal bridge from the cross bridge.