To provide a sheet opening holding tool which can be formed from one sheet, sufficiently keeps its function even if the sheet opening holding tool is prepared from a paper sheet, can be folded compact and is hardly folded when in use, while having an advertising effect.

This sheet opening holding tool is formed from a sheet that holds an openable/closable sheet in an opened state. The sheet opening holding tool includes: a top plate; a body constituted of a front side plate and/or a rear side plate connected to a front edge portion and/or a rear edge portion of the top plate via a fold; and a sheet pressing portion including at least two cutouts facing each other in a lateral direction toward a center of the top plate.