PURPOSE: To enable the production of a steel material having a circular section such as a round steel bar or the like with high production efficiency by rolling a continuously cast billet with a skew rolling mill having a specific angle of inclination and angle of crossing.

CONSTITUTION: A continuously cast billet 30 having center porosity is rolled as a material to be rolled with a skew rolling mill having 3W4 pieces of cone- shaped rolls 31, 32, 33. The rolls 31W33 have gorging parts 31aW33a, inlet surfaces 31bW33b and outlet surfaces 31cW33c, and the axial line X-Y thereof is inclined by an angle γ of crossing and an angle β of inclination to the pass line X-X of the material 30 to be rolled. The values γ, β are so set as to attain 0°<γ<15°, 3°<β<20°, 5°<γ+β<30°, whereby the center porosity of the billet 30 is press-stuck. Since the skew rolling mill is used to the continuously cast billet, the steel material having a circular section is rolled easily.