A sheet tray (1) includes at least one sheet detecting sensor (10) for detecting a sheet set on a sheet setting surface (2). The sheet detecting sensor (10) includes (i) a movable detecting section having a projecting section which projects from the sheet setting surface (2), and (ii) a detecting section for detecting rotation of the movable detecting section, and the projecting section have a ball-like shape. This makes it possible to provide (i) a sheet tray which is able to prevent breakage of sheet and breakage of the projecting section even when setting the sheet on the sheet setting surface from any direction and any angle; (ii) a sheet transporting apparatus including the sheet tray; and (iii) an image forming apparatus including the sheet tray.