The punched cardboard box is of the type delivered to the customers in a flattened condition and has a pair of opposite walls (A) already formed and a pair of opposite walls (B) to be formed connected to the walls (A) already formed by means of bellows tabs (29) foldable along an oblique folding line (12). The bellows tabs (29) have the function to produce the erection of the walls (A) already formed during the assembly of the box for obtaining a use configuration thereof. Each of said bellows tabs (29) has a tongue (30) projecting in the direction of the walls (B) to be formed and intended to be inwardly folded and to be glued against the end portions of the inner surface (19) of the adjacent wall (B) to be formed, so as to avoid the socalled "bag-effect" impairing the aesthetical appearance of the box, to resist to the lifting action exerted on the walls to be formed during the erection of the box, and to eliminate the differences in thickness during the glueing of the box in a flattened condition.