PURPOSE: To improve productivity and to manufacture a long-sized pipe by executing a hot rolling under the conditions that the heating temp. of the billet of titanium, the piercing ratio of an inclined piercing machine and the reeling times between a plug and roll satisfy a specific equation.

CONSTITUTION: A hollow pipe is manufactured from a solid billet 33 by the inclined piercing machine 40 equipped with plural inclined rolls. In this case, the heating temp. T0 of the titanium or titanium alloy billet 33 fed to the piercing machine 40, the piercing ratio El of the piercing machine 40 and the reeling times Rn between the plug 34 used for piercing and rolls 31, 31' are taken. The hot rolling is then completed by executing the piercing under the conditions satisfying the following relational inequalities 800°C≤T0≤1,050°C, 1.3≤El≤3.5, wherein, Rn≥1.2 in case of 1.3≤El≤2.5 and Rn≥1.4 in case of 2.5≤El≤3.5.