A radiation imaging apparatus comprising a detection unit for detecting a radiation distribution transmitted through an object, an imaging unit which includes the detection unit, and a grid for suppressing scattered light which is detachably mounted on an outside of the imaging unit, wherein the imaging unit includes a buffer member on a side surface facing a surface side which radiation strikes, the grid includes a grid body placed on the surface side which the radiation strikes, and a fixing unit for fixing the grid body to the imaging unit, and sides constituting the fixing unit include a side which does not protrude from an outer shape of the imaging unit when viewed from the surface side which the radiation strikes.