The present invention relates to a foldable step unit (10) for a rotorcraft, the step unit being provided with a bottom step (16) and a stationary support (11) that is secured to the structure of the rotorcraft (2). The step unit (10) comprises a left side beam (14) and a right beam (15) hinged on said stationary support (11), said bottom step (16) being arranged on a left free end (14′) and a right free end (15′) respectively of the left and right side beams (14, 15) via a pivot pin (16′), drive means (18) for said step unit (10) and connected via at least one control means (21, 22) to at least one side beam (14, 15) enable said step unit (10) to be retracted into and extended from a housing (2) formed in the rotorcraft (1).