PURPOSE: To simplify a process and to save a space by specifying the relation of an inclined angle and crossed angle, the diameter of a solid billet and the outer diameter, thickness of a hollow piece and specifying a piercing ratio, pipe extension ratio and thickness/outer diameter ratio.

CONSTITUTION: A solid billet 1 is pierced by the crossed type inclined piercing rolling mill on which three rolls are arranged to make a hollow piece 2. In this case, an inclined angle and crossed angle are taken in the range of 6°≤β≤20°, 3°≤γ≤35°, 12°≤β+γ≤50°. Also, the relation of the diameter d0 of the solid billet and the outer diameter (d), thickness (t) of the hollow piece of after piercing is taken as 1.2≤-γ/θ≤4.0, whereas γ=ln2t/d0, θ=ln2(d-t)/d0. The piercing is executed with the ≥3.5 piercing ratio {d02/4t(d-t)} or ≥1.5 pipe extension ratio d/d0 or ≤7% thickness/outer diameter ratio. Almost of all manufacturing process can be executed with one process and the seamless pipe making process is drastically simplified.