An X-ray detection technology capable of suppressing a decrease in a signal-to-noise ratio derived from external noise even in a case where it is hard to intercept electromagnetic-wave noise, and offering a wide dynamic range is realized, and an X-ray imaging device utilizing the technology is provided. An electromagnetic-wave noise signal to be mixed in a signal detected by an X-ray detector 2 is inferred from electromagnetic-wave noise signals measured by reference detectors 10A and 10B according to the method of least squares. Noise removal calculation is performed in order to minimize the decrease in a signal-to-noise ratio derived from the electromagnetic-wave noise.