1. A radiation image capturing system comprising: a plurality of image capturing apparatus of different specifications for capturing a radiation image of a subject; a plurality of processors disposed corresponding to each of the image capturing apparatus, the processors controlling the corresponding image capturing apparatus, respectively; a processor selector for selecting one processor from among the processors based on supplied image capturing instruction information; an image capturing condition setting unit for setting the image capturing conditions to be appropriate for an image capturing apparatus that is controlled by the processor selected by the processor selector among the plurality of image capturing apparatus; and an image capturing condition changer for, in a case where the image capturing apparatus is changed, changing the image capturing conditions to be appropriate for the changed image capturing apparatus, wherein the processor corresponding to the changed image capturing apparatus controls the changed image capturing apparatus according to the changed image capturing conditions.