Provided are a shutter piece, a shutter set, a shutter device, and a shape forming device which make it possible to gather an outer layer in an improved manner. A shutter piece (3) according to the present invention includes: an upper portion (13) of a first side surface (7) which seals a peripheral edge portion (DE) of an outer layer (D) over a filler (F) a lower portion (15) of the first side surface (7) which is positioned lower than the upper portion (13) and which, by contacting the outer layer (D) earlier than the upper portion (13), gathers the outer layer (D) toward the top of the filler (F) and an inclined surface (17) which is positioned lower than the upper portion (13) and which, when the upper portion (13) seals the peripheral edge portion (DE) of the outer layer (D), formspart of a spindle-shaped space above the filler (F).本發明提供一種改善外皮材聚集的百葉片、百葉組、百葉裝置及成形裝置。本發明的百葉片(3),具有:第1側面(7)的上側部份(13),以內材(F)的上方封閉外皮材(D)的周緣部(DE);第1側面(7)的下側部份(15),位在比上側部份(13)下方且在上側部份(13)之前與外皮材(D)接觸將外皮材(D)朝內材(F)的上方聚集;及傾斜面(17),位在比上側部份(13)下方且上側部份(13)封閉外皮材(D)的周緣部(DE)時在內材(F)的上方形成錘形空間的一部份。3c‧‧‧前端緣3e‧‧‧下端7‧‧‧開口側面9e‧‧‧前端13‧‧‧上側部份(第1側面)13a‧‧‧上緣(周緣)15‧‧‧下側部份(第2側面)15a‧‧‧下緣(突出緣)15b‧‧‧前端17‧‧‧三角形側面(第3側面)
