To provide a method for producing a polymer hydride by which aromatic rings of an addition polymer of an aromatic vinyl monomer can be hydrogenated in a high ratio and the decomposition reaction accompanied with the hydrogenation is suppressed to scarcely lower the molecular weight and broaden the molecular weight distribution.

A polymer having unsaturated bonds is hydrogenated by increasing hydrogen pressure to a pressure within the range of 1-2.4MPa, increasing the temperature to a temperature within the range of 100-155°C and simultaneously increasing the hydrogen pressure to a pressure while controlling the temperature of a reaction liquid containing the polymer having the unsaturated bonds to a temperature within the range of 40-90°C. After the hydrogen pressure reaches the pressure within the range of 3.5-4.3MPa, the temperature is increased to a temperature within the range of 160-200°C and the pressure is increased to a pressure within the range of 4.3-6MPa.