A speed measuring device for a rotating body is disclosed, in which a correction coefficient is used to correct a measurement error in each of a plurality of pulse signal durations which represent speed data of the rotating body. The correction coefficient is updated in order to exclude a deviation in the corresponding pulse signal duration caused by an abnormal state of the rotating body. For this purpose, the first step is to determine a mean value of the pulse signal durations corresponding to a revolution of the rotating body, whereupon a value is determined which specifies a deviation between a respectively corresponding pulse signal duration and the mean value. Furthermore, an updating value is derived by using a correction sensitivity coefficient to set a parameter of the value specifying the deviation to the correction coefficient. The correction coefficient is updated by adding the updating value to a last value of the correction coefficient.
