A sheet width regulating device includes a base plate, a regulating member, a first moving cursor, a first guiding portion, a second guiding portion, a first guidable portion, a second guidable portion, and a synchronizing member. The regulating member regulates one end of the sheet. The first moving cursor regulates the other end of the sheet, and is movable in the way perpendicular to a direction along the other end of the sheet that the first guiding portion extends. The second guiding portion extends in parallel with the first guiding portion. The first guidable portion is attached to the first moving cursor and guided by the first guiding portion. The second guidable portion is attached to the first moving cursor and guided by the second guiding portion. The synchronizing member synchronizes a movement of the first guidable portion and the second guidable portion.