In a method for testing the thermally induced unbalance of a rotating machine part, in particular the rotor of a turbogenerator, the rotating machine part or the rotor balanced at normal temperature is brought in the demounted state first to nominal rotational speed and held at this, while its temperature is varied and, at the same time, the transient variations in oscillations of the rotating machine part or rotor which are caused are measured. During the test, the rotating machine part or the rotor is surrounded at least partially by a closed heating cell, a cooling medium flows around and/or flows through the rotating machine part or the rotor in the heating cell, and the heating of the rotating machine part or of the rotor takes place essentially due to the flow-dynamic losses arising from the interaction of the rotating machine part or of the rotor with the circulating cooling medium.