An X-ray detection signal processing apparatus of the present invention is such that after a signal from a preamplifier has been converted into a digital signal at a high speed by means of a high speed analog-to-digital converter (1), a process for removing influences brought about by a component that has been decayed by a differential time constant in the preamplifier is performed on a digital basis in a digital signal processing block (2). An event detecting unit (3) within the digital signal processing block (2), smoothen the signal from the high speed analog-to-digital converter (1) for a predetermined shaping time with the use of a filter function for high speed shaping, detects as an event information the timing at which the smoothened signal exceeds a predetermined threshold and attains the maximum value, and add such event information to the signal from the high speed analog-to-digital converter (1).