With a mammography PET apparatus, a supporting face includes a detector ring region, and a detector-outside region as an outside area of the detector ring region. The detector ring region is higher than the detector-outside region. An elastic lower-layer mat is disposed on the detector-outside region. An upper-layer mat, softer than the lower-layer mat, is disposed on the detector ring region and the lower-layer mat across a boundary between the detector ring region and the lower-layer mat. Accordingly, an edge of the lower-layer mat harder than the upper-layer mat is covered with the upper-layer mat, leading to alleviation of pain to a subject M caused by the edge of the lower-layer mat.
