The present invention concerns a tubular rock bolt (1) that can be expanded by a pressurised medium, for insertion into a drilled hole (16) and comprising an extended tubular part (2) with a closed cross-section (12) and provided with a longitudinal stamped part (13) that increases in diameter during the expansion of the rock bolt (1) without the periphery of the tubular part (2) being bent, and an end section (17) at one end (15) of the rock bolt (1) and an end piece (19) arranged at the second end (18) of the rock bolt (1) and provided with a connection part (22) for interaction in a manner that can be released with an expansion means (23). The extended tubular part (2) comprises a reinforcement means (3) that extends internally inside the tubular part (2) between the end section (17) and the end piece (19) and that is attached at the end section (17) and the end piece (19). The invention concerns also the manufacture of a rock bolt.