Abstract: When an image for PET attenuation correction is generated from an MR image, the MR image captured by MRI is segmented into regions according to pixel values. In a region in which a radiation attenuation coefficient is considered to be uniform, a radiation attenuation correction value is determined by referring to an existing radiation attenuation correction value table. In a region including multiple tissues having different radiation attenuation coefficients, a radiation attenuation correction value is determined by referring to a standard image. In such a manner, an image for PET attenuation correction in which tissues having similar pixel values in the MR image but different attenuation coefficients for radiation can be distinguished and that can accommodate individual differences and an affected area such as a space occupying lesion (for example, a cancer, abscess, or the like) and an organic defect is generated.