Provided are an image synthesizing device and an image synthesizing method wherein a subject is less affected by beam absorption. A diffraction beam intensity and a front diffraction beam intensity actually detected are included in the influence of absorption on a subject (Sa). Yet, assuming that said beams have the attenuation rate which is caused by said beams being absorbed when passing through a subject, the angle of refraction θ0 of the beam when passing through the subject (Sa) is obtained using the diffraction beam intensity and the front diffraction beam intensity which are not affected by attenuation, and which are represented by the aforementioned attenuation rate, front diffraction beam intensity, and diffraction beam intensity a synthesized image of the subject (Sa) is obtained by means of said angle of refraction θ0.
