For easy determination of the current stress condition of a person, a device is proposed that detects the pulse rate and therefrom additionally determines the heart rate variability—preferably by means of a fast Fourier transform. In addition, at least one parameter related to the history of one of the two values mentioned above shall be used. Preferably, the deviations of the cardiac frequency and of the heart rate variability from corresponding norm parameters are integrated and thus used as an additional stress indicator.