Abstract: What is proposed is an apparatus for automatic catalyst exchange in a plurality of process steps in the catalyst tubes of a reactor with a bundle of catalyst tubes, which are welded in or rolled in between an upper tube plate and a lower tube plate in longitudinal direction of the reactor, and welded tight, comprising a tool carrier device, which is arranged so as to be mobile in a plane above and parallel to the upper tube plate, and which can be equipped with an exchangeable tool for each process step, the exchangeable tool being mobile together with the tool carrier device in the plane above and parallel to the upper tube plate and also vertically, in the direction of the longitudinal axis of the reactor, and being able to access each individual catalyst tube with control by means of a control unit, the position of the longitudinal axis of each individual catalyst tube being measured or calculated and recorded in the control unit in a position database.