A mammogram recording and read-out apparatus comprises a radiation image detector having a rectangular shape, a detector support section, and a breast support section. A support state of the detector support section is capable of being changed over between a first support state, in which the radiation image detector is supported in an orientation such that a short side of the radiation image detector stands facing the chest wall of an object, and a second support state, in which the radiation image detector is supported in an orientation such that a long side of the radiation image detector stands facing the chest wall of the object.