Device for mounting and demounting of a probe to be arranged in an access tube to a process pipeline, including a hydraulic cylinder accessing the access tube with a gripping tool to engage a probe for moving this probe into an operating position in the access tube and retrieving the probe from this position. A revolving unit with at least two chambers is provided, each chamber accommodating an axially movable probe. The chambers are accessible by the gripping tool to move a probe into a chamber and, in a subsequent step, from the chamber into the access tube. A powering device is arranged for revolving the revolving unit.