An apparatus for finishing products coming out from a folding and gluing machine of cardboard or paperboard products with a back, includes a longitudinal housing for advancing the products in rows, defined by two groups (40, 41) of circular motorized right and left belts. Each group (40, 41) being made of at least three belts. An upper belt (22, 24) and a lower belt (25, 27) are wrapped around pulleys with a horizontal axis and extending parallel to the direction of advancement of the products. A lateral belt (28, 29) is wrapped around pulleys with a vertical axis and extending parallel to the direction of advancement of the products. The belts of each group (40, 41) form among them respective “C”-shaped housing which make the lateral edges of the housing along and inside which the product advances, dragged by the belts.