a method of monitoring abnormality of a clock driver in an electronic apparatus having a clock supply unit that supplies a clock signal and a plurality of function executing units to which the clock signal is inputted for executing prescribed functions at an identical clock , wherein each function executing unit is provided with a clock driver which , on the basis of the clock signal , oscillates internally to reproduce a clock signal , includes monitoring cut - off of an input clock signal and cut - off of an output clock signal of the clock driver , and outputting an alarm upon judging that the clock driver is abnormal in a case where the output clock signal has been cut off but the input clock signal has not . alternatively , the method includes monitoring the phase of the input clock signal and the phase of the output clock signal of the clock driver , and outputting an alarm upon judging that the clock driver is abnormal in a case where the output clock signal has developed a phase shift , which is greater than a prescribed value , with respect to the input clock signal .