A radiation image capturing system includes a radiation image capturing apparatus, an irradiation apparatus and an image processing apparatus. The image processing apparatus generates a first radiation image of a subject based on a signal value generated by the radiation image capturing apparatus with no grid attached irradiated by the irradiation apparatus; performs a low-pass filter process on a pixel value of the first radiation image using a scattering kernel, thereby generating a low frequency image; estimates a body thickness of the subject based on the signal value; estimates a scattered ray content rate based on the body thickness; calculates a scattered ray component in the first radiation image based on the low frequency image and the scattered ray content rate; and subtracts the scattered ray component from the first radiation image, thereby generating a second radiation image.