To make correct determination of electric charge collection among signals from a semiconductor radiation detector, provided in an embodiment of the present invention is a signal data processing method. The method includes a step of calculating timing data sequences unique to channels (timing data calculation step S02), each of channels corresponding to each of plural electrodes of the radiation detector, from detection signal data sequences. Then, while making a comparison with a first threshold value, a data value for the timing data sequence at timing when a predetermined delay time is elapsed after the timing data sequence reached the first predetermined value is selected as a timing data value for determination for the channel (delay and selection step S04). Finally, by comparing the timing data value for determinations for channels with a second threshold value, a detection signal data sequence greater than or equal to the second threshold value is determined to be a detection signal data sequence for a channel that actually collected the electric charge (determination step S06). In embodiments of the present invention a signal data processing device and radiation detection system are also provided.