To provide an opening/closing type grille for windows, which is prevented from protruding to the outdoor side of the window by being installed on the indoor side of a window sash, which can maintain the beauty of the appearance of a window part, and which is equipped with an easily operable and safe locking device.

This opening/closing type grille 20 for the windows is installed on the indoor side of the window sash. The locking device R for inhibiting a grille member from moving to a storage part side in the closing of the grille for windows is equipped with: a locking member 61 which comprises a first protrusion 65B and a second protrusion 65A; a stopper 67 which is engaged with the locking member so as to inhibit the turning of the locking member, when the locking member inhibits the movement of the grille member; and a safety stopper 111 which inhibits the turning of the locking member when the stopper is disengaged from the locking member, and which releases the inhibition of the turning of the locking member by the operation of the movement of the grille member at a leading end to the opposite side of a screen part.