To efficiently reduce a pipe by heating a pipe stock of large diameter while rotated, drawing it through a reduction roll to reduce the pipe stock to the prescribed diameter, controlling the drawing speed and the rotational speed according to the diameter for reduction, and heating and keeping the pipe at the temperature balanced for the heating and optimum for the drawing.

In working a pipe, a heater 4 of a pipe reducing device 1 is heated to and kept at the prescribed temperature. A pipe stock W is inserted in the heater 4, a tip is supported by a chuck 22 of a spindle 6, and rotated at the prescribed speed by a motor 23 of the spindle 6. As the stock W is heated, a motor 24 for driving a spindle traveling bed of the spindle 6 is operated, and the reduction is achieved by simultaneously advancing three reduction rolls of a reduction mechanism 5 as soon as the drawing. The diameter of reduction is controlled by a control mechanism 30 of a position detector of the reduction rolls mounted on the reduction rolls. The transfer speed of the spindle 6 is increased according to the diameter of reduction. The rotational speed of the stock W is also increased thereby.