To keep the gap between a nozzle end part and a side weir plate constant.

A twin roll casting apparatus is constituted of one pair of parallel casting rolls 16, and molten metal is supplied through a distributor 18 into the rolls and the nozzle 19 for supplying the molten metal to form a casting pool part constituted of the side weir plates 56 supported with the casting rolls 16. The side weir plate 56 leans to the end surfaces of the casting rolls 16 so as to be movable inward in adaptation to the wear of the side weir plate 56. The nozzle 19 is formed of slender nozzle pieces 19A arranged in the facing state to the end parts thereof and separating state. Since the projection 71 at the outer end of the nozzle 19 is engaged with the side weir plate 56, the nozzle piece 19A is shifted inward with the side weir plate 56 to keep the gap between the side weir plate 56 and the nozzle end part constant. The projection 71 can be replaced with a pusher element extendably separated between the nozzle end part and the side weir plate 56 or a plate holder 72.