A machine for forming boxes which have at least a main body with the possibility of also having a lid hinged to it, from flat blanks, comprises a carousel (4) rotating about its own axis of rotation (4a), a plurality of pick up and transfer arms (5) mounted radially on the carousel (4) and able to rotate with it about the axis of rotation (4a) and a plurality of operating stations (6, 8, 9, 10) positioned along a circular path (P) described by the arms (5). The operating stations comprise at least a pick up station (6) for the blanks (3), a gumming station (8), a folding station (9) and a station (10) for releasing the at least partly formed boxes. Each arm (5) comprises a pick up element (11) able to slide radially away from the carousel (4) to pick up the blank (3) directly from the pick up station (6) and to accompany the box (2) as far as a supporting surface (15) at the releasing station (10).