PURPOSE: To prevent impurities from entering at the time of unpacking, to easily and quickly perform unpacking and to perform rigid and reliable closing.

CONSTITUTION: An apparatus for closing a bag including a pair of front and rear endless carrier chains 2 for carrying a bag 1 filled with contents and a taping mechanism 14 for taping an upper end 1a of the bag 1 carried by the chains 2 into a horse shape is equipped with a folding mechanism 11 for folding back the upper end 1a of the bag 1 at a main body position prior to the taping mechanism 14. The folding mechanism 11 comprises a pair of front and rear rollers 12 for making a fold line 1b horizontally on the upper end 1a and a folding former 13 for folding back the upper end 1a via the line 1b made by the rollers 12. The roller 12 comprises a roller 12A with an edge 12a formed like a flange on a peripheral face and another roller 12B formed on the peripheral face with a circular groove 12b with which the edge 12a is engaged.