There is provided a configuration that allows implementation of both photon measurement and current measurement with practical measuring performance and circuit area, where a plurality of detector elements constituting one detector pixel are connected to photon measuring circuits on a one-to-one basis, thereby counting current pulse signals outputted from the detector elements, and a current measuring unit incorporates an integrator, an adder, and a sample-hold circuit provided for every detector pixel, and a converter for converting analogue signals to digital signals, one converter being provided for a plurality of detector pixels. The integrator integrates and the adder adds current pulse signals respectively outputted from the plurality of detector elements constituting one detector pixel, the sample-hold circuit integrates outputs from the adder, and the converter selectively converts analogue outputs from the integration circuit of any of the plurality of detector pixels.
