It is an object to form a plate for a sliding nozzle apparatus in a shape for decreasing extreme erosion and extend durability of the plate to enable cost reduction, the sliding-nozzle plate having dimensions (unit length is mm) as indicated in following equations: a dimension from the center position X of the nozzle hole to a closest end of the plate for the sliding nozzle in the longitudinal direction is a sum of a dimension “b” from the center position X to an ideal circle with the position X as the center and a dimension “d” from the ideal circle to the closest end in the longitudinal direction, a dimension from the center position X and to a center position Y is a dimension S of the stroke, and a dimension from the center position Y to a closest end of the plate for the sliding nozzle in the longitudinal direction is a dimension “c”, where b: a+30˜40, c: 0.75a+20˜30, d:0.5a, S:2a+m, and m:15˜35.