To provide a method for manufacturing a hydrogenated polymer which comprises a step of estimating the melt index value of the hydrogenated polymer to be produced by the hydrogenation of an unsaturated polymer with high precision based at least on the molecular weight of the unsaturated polymer as one factor, and a method of manufacturing the hydrogenated polymer having a target melt index by controlling the reaction conditions based on the above estimation.

The method for manufacturing the hydrogenated polymer comprises hydrogenating the unsaturated polymer having a carbon - carbon unsaturated bond in the molecule, and the manufacturing method comprises a conversion step of collecting the unsaturated polymer during the period of from after completion of the polymerization step to immediately before the hydrogenation step, measuring at least the molecular weight of the unsaturated polymer as one of the properties of the collected unsaturated polymer and the reaction conditions, and converting at least the measured value of the molecular weight of the unsaturated polymer into a melt index value of the hydrogenated polymer to be obtained by the hydrogenation step on the basis of the previously found relationship between at least the molecular weight of the unsaturated polymer and the melt index of the hydrogenated polymer to be obtained by the hydrogenation of the unsaturated polymer.