An apparatus for folding in two a continuous web (10) that advances in a longitudinal direction (A), comprising: a folding station (22) designed to fold said continuous web (10) along a line of longitudinal folding (B) parallel to said longitudinal direction (A) and an alignment station (24) for mutual alignment of opposite longitudinal edges (14) of said continuous web (10), wherein said alignment station (24) comprises two suction belt conveyors (42, 44) having respective branches facing one another (50, 52) designed to pick up by means of suction respective folded sections (34, 32) of said web (10), said suction belt conveyors (42, 44) being mobile in a transverse direction (D) and being associated to a control device (72) designed to move said suction belt conveyors (42, 44) by the same amount and in opposite directions in said transverse direction (D) as a function of information on the position of said longitudinal edges (14).
