The present invention is to facilitate the attachment and maintenance work of left and right sheet guides of a shutter and to facilitate the return of the disengaged sheet. A sheet guide of a sheet shutter according to the present invention is a mechanism configured such that a sheet 2 is lifted and lowered by being wound and unwound around a sheet drum 5 supported between left and right support posts 3 and 3 according to the rotation of the sheet drum 5, and such that both the left and right ends of the sheet 2 are lifted and lowered by being guided by sheet guide sections 11 and 11 respectively installed in the support posts 3 and 3. The sheet guide section 11 is configured by an outer rail 14 having a U-shaped cross section which is provided with a pair of front and rear side walls 14a and is opened toward the inner side in the horizontal cross section of the left and right support posts 3, and an inner rail 16 accommodated and detachably attached in the outer rail 14 along the inner surface of the outer rail 14. An inward-facing engagement guide 21 configured to vertically slidably and engagingly accommodate each of guide projections 10 respectively attached to both ends of the sheet 2 is provided in the inner rail 16.