Abstract: The present invention provides an apparatus for handling core constituent elements of a reactor that comprises a core having as core constituent elements control rod assemblies each containing a control rod and fuel assemblies each containing nuclear fuel, a small rotating plug rotatably provided on the core, and a control rod drive mechanism provided on the small rotating plug, the control rod drive mechanism being characterized by comprising a plurality of grippers each having a hook projecting inwards so as to be able to engage with a handling head of the control rod and a hook projecting outwards so as to be able to engage with a handling head of each of the core constituent elements as a distance in the longitudinal direction; an operational head for opening and closing the grippers; and a third elevating drive mechanism for vertically driving the operational head; a second elevating frame for supporting the third elevating drive mechanism and the grippers; a second elevating drive mechanism for vertical