Provided is a radiation detecting apparatus, including: a radiation detector arranged to detect radiation; an electrical circuit board configured to control the radiation detector; a cooling unit arranged to cool the radiation detector and the electrical circuit board; and a casing arranged to accommodate the radiation detector, the electrical circuit board, and the cooling unit therein, in which at least an outer surface of the casing has a recessed portion that is recessed across a back surface portion, which is on an opposite side to a side in which the radiation enters, and a lateral surface portion adjacent to the back surface portion, and in which the recessed portion has lead-out portions formed therein, through which a wiring line removably connectable to the electrical circuit board and a piping line arranged to allow a cooling medium to flow to the cooling unit are respectively led out external to the casing.