A sheet post-processing apparatus (1) includes a first stapler (4) and a second stapler (5) for stapling the stack of sheets on a stack tray (61), a first moving frame member (10) on which the first stapler (4) is mounted rotatably, a second moving frame member (11) on which the second stapler (5) is mounted, a rotating member (20) rotatably mounted on the first moving frame member (10), the rotating member (20) so held in engagement with the first moving frame member (10) as to move linearly the first moving frame member (10) by rotation of the rotating member (20), and also rotating the first stapler (4) by rotation of the rotating member (20), and a single drive power source (16) for driving the rotating member (20).