PURPOSE: To prevent a grating from freezing at a snow throwing port and being in a stuck state.

CONSTITUTION: A grating 2 is furnished with a side plate 7 supported free to revolve around a horizontal shaft part 6 as its center and free to open and close.from an open position along a side wall inner surface 4 of a snow throwing port 1 to a closing position to separate from the side wall inner surface 4 of the snow throwing port 1 and a side plate opening and closing mechanism 8 to open and close this side plate 7. At the time of non-snow removal, the side plate 7 is set in the open position to open toward both sides of a grating main body 5 and set along the side wall inner surface 4 of the snow throwing port 1, and at the time of using the snow throwing port l, a revolving member 9 of the side plate opening and closing mechanism 8 is revolved, the both side side plates 7 are set in the closing state along both side surfaces of the grating main body 5, and the side plates 7 of the grating 2 are separated from the side wall inner surface 4 of the snow throwing port 1. Even when the grating 2 is frozen with snow and an ice X, these spaces break the frozen ice.