Abstract: In a method and apparatus of making the bottom of a flat tubular section, a tubular section is transported by a conveyor at a continuous rate in an alignment transversely to a longitudinal direction of the conveyor, with a first suction unit partially opening one end of the tubular section. Subsequently, a spreader unit is inserted into the partially open end of the tubular section and moved in a first phase in a substantially linear horizontal motion toward an end position in which the spreading unit conforms to fold lines of a finished bag bottom. In a second phase, the spreader unit swings from a substantially horizontal alignment into a substantially vertical position about a horizontal pivot axis by way of a compound motion in which a movement of the spreading unit into the end position is superimposed by a movement into the vertical position, thereby forming the open bag bottom.