Side wing adjustment mechanism and adjustable sitting device

A side wing adjustment mechanism and an adjustable sitting device, the side wing adjustment mechanism includes: a pin arranged on the headrest; and an inclined grooves arranged on the side wing, a distance between a portion of the inclined grooves and the longitudinal center axis gradually decreases in a direction extending from bottom to top toward the headrest along a longitudinal center axis of the backrest, and the pin is slidable along the inclined grooves. According to the application, the side wing can be folded and opened at will, and the structure of the application is more inclusive. During the opening and folding process, puling of the headrest or pushing of the side wing can be performed more smoothly and labor-savingly, and the phenomenon of deflection and jamming can be avoided, such that the opening and folding process of the side wings is smoother.