A top roller, which is difficult for a flow path for cooling water to be narrowed or clogged therein, and which is capable of properly working for a long period of time, is provided. A top roller comprising a rotatable leading edge portion, which is adapted to be used for controlling the shrinkage of a molten glass ribbon in a float bath and to be brought into contact with the molten glass ribbon, the leading edge portion having a hollow structure including a leading edge space therein; wherein cooling water having a hardness of at most 100 (mg/L) passes through the leading edge space.