1. An X-ray imaging method using an X-ray imaging device that includes a scintillator, one surface of which is an X-ray incident surface and which generates scintillating light in accordance with incident X-rays to convert an X-ray image to an optical image, and an imaging element, which is disposed so as to face the other surface of the scintillator and detects the optical image generated by the scintillator to acquire an X-ray observed image corresponding to the X-ray image made incident on the scintillator, and comprising: a first image acquisition step of acquiring, by means of the X-ray imaging device, a first X-ray observed image that contains an image component, corresponding to the X-ray image converted to the optical image by the scintillator, and a first noise image component, due to X-rays made directly incident on the imaging element; a second image acquisition step of acquiring a second X-ray observed image that contains a second noise image component differing from the first noise image component; a subtraction processing step of performing a subtraction process between the first X-ray observed image and the second X-ray observed image to generate a noise image into which the noise image components are extracted; a threshold value processing step of performing a threshold value process on the noise image to extract the first noise image component among the noise image components; and a noise removal step of subtracting the first noise image component, extracted in the threshold value processing step, from the first X-ray observed image that contains the first noise image component to generate a noise-removed image, with which the first noise image component is removed.