A seamless steel tube for air bag use is formed from a steel comprising, in mass percent, C: 0.04-0.20%, Si: 0.10-0.50%, Mn: 0.10-1.00%, P: at most 0.025%, S: at most 0.005%, Al: at most 0.10%, Cr: 0.01-0.50%, Cu: 0.01-0.50%, Ni: 0.01-0.50%, a remainder of Fe and unavoidable impurities. The tube is cold drawn at least one time with a working ratio so that reduction in area is greater than 40% to obtain predetermined dimensions. The tube is then quench hardened by heating to at least the Ac3 point at a temperature rate increase of at least 50° C. per second followed by cooling at a cooling rate of at least 50° C. per second at least in a temperature range of 850-500° C. Tempering is done at a temperature of at most the Ac1 point.