To drill a hollow pipe whose thickness nonuniformity is suppressed by using specific values for the distance between an inclined roll center and a mandrel holding device adjacent to the inclined roll, distance between mutually adjacent mandrel holding devices, and the ratio of these distances to the diameter of solid material and setting the ratio of the cross-sectional area of the mandrel to the cross-sectional area of the maximum outside diameter portion of the plug in a specific range.

A distance L1 between the center of an inclined roll 1 and a mandrel holding device 5A adjacent to the inclined roll 1 and a distance L2 between the mutually adjacent mandrel holding devices 5A and 5B are made to be 0.8-3.5 m. The ratio (L1/Bd) of the distance L1 to the diameter (Bd) of a solid material 6 and the ratio (L2/Bd) of the distance L2 to the diameter (Bd) of the solid material 6 are made to be 25 or less. The ratio of the cross-sectional area of the mandrel 4 to the cross-sectional area of maximum outside diameter portion of a plug 2 is made to be 0.5-0.98. It is preferable that the outside diameter of the mandrel 4 is made to be 95% or lower of the inside diameter of the hollow pipe 7 or 98% or less of the maximum diameter of the plug 2.