To provide a sliding mechanism of a mounting base enabling a mounting base to be moved to the center of a bed after putting a stretcher alongside the bed.

The sliding mechanism is configured in such a way that a sliding frame formed in substantially U-shape in plan view is formed on a base frame, a bottom frame is formed on the sliding frame, a drive means and an interlocking mechanism are formed on the slide frame, a sliding frame support plate constituting the interlocking mechanism is fixedly attached to the base frame and a coupling member is fixedly attached to the bottom frame. The sliding frame slides on the base frame and the bottom frame slides on the sliding frame, and thus the configuration enables sliding longer than the width of the bottom frame.