An X-ray imaging system is constituted of: an X-ray imaging device that includes a scintillator, which converts an X-ray image to an optical image, and an imaging element, which acquires an X-ray observed image by detecting the optical image generated by the scintillator; a first subtracter that performs a subtraction process between a first X-ray observed image, which contains a first noise image component, and a second X-ray observed image, which contains a second noise image component, to generate a noise image; a threshold value processing circuit that performs a threshold value process on the noise image to extract the first noise image component; and a second subtracter that subtracts the extracted first noise image component, from the first X-ray observed image to generate a noise- removed image.