A laminate tube with an invisible longitudinal overlapped side seam formed from overlap welding an edge of one margin of a laminate sheet comprising an outer plastic layer (A), a barrier layer (B), and an inner plastic layer (C) of the same material type as the outer plastic layer (A) to the other edge of the opposite margin of the laminate sheet, such that an inner surface of the laminate tube has a hump in a overlapped region, while an outer surface of the laminate tube is smooth without a hump in the overlapped region; and a process for manufacturing the laminate tube by a laminate tube manufacturing machine. The laminate permits fracture-proof welding of longitudinal margins of said laminate to give a continuous tube which is suitable for manufacturing of high-quality plastic tubes, high-quality plastic bags and the like.