a preamp 2 for converting the generated current pulse to a voltage pulse and the voltage pulse is input to the x ray counting section at the x ray counter section for a single input a plurality of signal processing sections 5 are operating simultaneously however these sections have respectively different processing times and a favorable energy resolution is obtained with systems having quite long processing times but the probability of adjacent pulses overlapping in time is high output from these signal processing systems is sent to a signal selecting section 6 and which signal processing system 39 s value is to be used is determined based on an output value of a signal processing system having the shortest processing time that is the system acquiring results in the quickest time data constituting a reference for determination namely data indicating correspondence between energy and the signal processing sections can be set from a data processing section 4 also with an energy dispersive x ray analyzer having restricted application it is possible to have an embodiment having a fixed judgment reference in the x ray counting section without going through the data processing section by performing selection in this way data of a particular signal processor is sent to a multi channel analyzer 7 by repeating this process an energy spectrum of x rays incident to the detector is acquired and the data processing section 4 performs processing according to the purpose of use the operation of an energy dispersive x ray analyzer of the present invention has been outlined above next an x ray counting section of.