A radiation image capturing system capable of improving image quality of a radiation image is provided. A position of a joint of a grid is determined in consideration of displacement of an angle of incidence of radiation on a grid unit and a radiation detector group, and a joint image caused by the joint of the grid is prevented from being included in a search range of a position of a boundary in the radiation image captured by the radiation detector. The joint of the grid is provided in a position away ±(y1+2×y2)×tanβ or more from a position of a step of the radiation detector.
