The invention discloses a gear slotting machine capable of being adjusted. The gear slotting machine comprises a bed body, wherein a base is arranged on one side of the bed body; the upper side of the base is connected to one end of a vertical shaft while the other end of the vertical shaft is connected to one end of a movable piece; the other end of the movable piece is connected to one end of an operating shaft; a connecting hole is formed on the movable piece; the other end of the operating shaft is connected to a gear slotting shaft; a gear slotting cutter is arranged on the gear slotting shaft; an adjusting piece is arranged on the other side of the bed body; a horizontal worktable is arranged above the adjusting piece; and a fixed part is arranged on the horizontal worktable. The gear slotting machine capable of being adjusted machines a helical face gear through a cylindrical gear slotting machine, so that on the one hand, purchase of expensive equipment is avoided and the machining cost of the helical face gear can be lowered; and on the other hand, the machining efficiency of the helical face gear is relatively improved, and the production cost of an enterprise is lowered; according to a gear slotting design which is movably adjusted, a user can adjust the angle as required, so that the gear slotting machine is time- and labor-saving and is flexible and variable.