PURPOSE: To prevent a shaking of a sash and the invasion of rain water securely and to improve the operating efficiency by fixing a sash at plural restricting points by locking bodies and locking members, and tightening another sash by engaging the locking bodies and engaging metals.

CONSTITUTION: A locking mechanism 15 which consists of a case 24, a slide frame 25, locking bodies 21, and a cam mechanism 26 is installed to a sash 3. And the reciprocating operation of the slide frame 25 is converted to a reciprocating operation in the direction crossing to the operation direction by the cam mechanism 26, and the locking bodies 21 are slide-moved simultaneously with the slide frame 25 and composed engageable to the engaging metals 22 of the sash 2. And the locking mechanism 15 and the locking members 16 and 17 are made lockable by one touch operation of a single operating handle 19 through transmitting members 18. Furthermore, the sash 3 is fixed movable at least at two restricting points, and a sash 2 is tightened by the sliding operation of the locking bodies 21.