The machine is designed to form pallets by assembling cardboard longitudinal beams (1) and transverse beams (2) comprising means for storage, feed and dosing of longitudinal beams (1) and with means for storage, feed and dosing of transverse beams (2), means provided at corresponding areas (4, 5) for placing the longitudinal beams (1) longitudinally edgewise and coupling transversally thereto the corresponding transverse beams (2), both being provided with complementary notches for assembling the same. The longitudinal beams (1) from the area (4) are displaced on rails (16) and are situated in the area (5) where the transverse beams (2) fall and are pushed vertically by a pusher (22) to assemble the transverse beams (2) onto the longitudinal beams (1) previously and appropriately placed in the area.