PURPOSE: To obtain the title device smoothly controlling rotation of a shield without sliding and bringing the shield into contact with a helmet material side, by simply and rapidly removing the shield from a dent part so as to independently operate a rotation controlling mechanism and a widening and shorting width mechanism.

CONSTITUTION: When a shield 4 is transferred forward from a wholly closed position by a finger F, the shield is guided and transferred forward by a longitudinally moving mechanism 5, the end part of the shield is widened sideways by gearing of a widening and shortening width mechanism and the shield is removed from a dent part. When the shield reaches the most front position, namely an open position, a rotation controlling mechanism (pivoting mechanism 7 and clicking mechanism 8) can be worked and an angle of rotation can be regulated by rotating the shield in the vertical direction.