To eliminate the development of turbulent flow of an opening hole part caused by the collision of molten metal against a lower nozzle by adjusting the opening hole parts of a slide plate and the lower nozzle so as to form as straight flow when molten metal is made to flow down at the opening hole parts.

In a sliding nozzle apparatus constituted of a fixed plate in contact with an nozzle disposed at the bottom part of a vessel for holding the molten metal, the slide plate and the lower nozzle in connection with this slide plate, the straight flow type flow rate control apparatus for molten metal is provided with a straightening plate constituted of the following members disposed between the fixed plate and the slide plate. The above members are (a) a first control plate arranged so as to be slidable for adjusting the opening area in the opening hole part between the fixed plate and the slide plate and a second control plate disposed so as to be faced to the first control plate, and (b) two pieces of pushing plates disposed so as to interpose from both sides of the first and the second control plates which are slidable.