The present invention is one that removes noise of a voltage signal to be inputted to a pulse processor 5, as well as improves radiation energy resolution, and includes: a radiation detector 2 that outputs charge generated by incidence of radiation; a preamplifier 3 that converts the generated charge into an analog signal; an A/D conversion part 4 that converts the analog signal from the preamplifier 3 into a digital signal; a denoising filter 5 that removes the noise from the digital signal from the A/D conversion part 4; a waveform shaping part 6 that generates a pulse signal from a digital signal having passed through the denoising filter 5; a pulse height detection part 7 that detects peak values of the pulse signal from the waveform shaping part 6; and a count part 8 that, on a pulse height basis, counts the peak values obtained by the pulse height detection part 7, in which the denoising filter 5 is one that removes the noise by taking the weighted moving average of values of the digital signal with use of a weighting factor depending on the difference from a predetermined reference value.