Automatic folding mechanism and method and sleeve placket sewing device

The invention provides an automatic folding mechanism and method and a sleeve placket sewing device. The automatic folding mechanism comprises a fixing base plate, a discharging plate, a baffle assembly, a discharging cavity formed by the discharging plate and the baffle assembly, a turnover clamping assembly located in the discharging cavity and a fold material shifting piece. One end of the discharging cavity is provided with a sleeve placket end forming part, a plurality of first suction holes distributed in the peripheral direction of the discharging cavity at intervals are formed in the discharging plate, the clamping assembly comprises a movable clamping plate and a fixed clamping plate which are stacked, and a clamping cavity formed in the movable clamping plate and the fixed clamping plate, the movable clamping plate can move close to or away from the fixed clamping plate, the fold material shifting piece is located at the upper side of the baffle assembly and can move close toor away from the sleeve