To carry out continuous hot drawing with high reliability without any fear of causing bending, etc., in a preform by tilting the rotational direction of caterpillars performing the tensile stretching together with moving operations of a lower gripping part on the lower end side of the optical fiber preform to a prescribed angle to the preform axial line direction.

The top side of an optical fiber preform 100 is held with an upper chuck 2 and the lower end side of the optical fiber preform 100 is held with a lower chuck 3. A pair of a left and a right caterpillars 1 carrying out the tensile stretching of the optical fiber preform 100 together with moving operations of the lower chuck 3 are installed in a state thereof tilted from the drawing axial direction of the optical fiber preform 100. The upper chuck 2 and the lower chuck 3 are rotated at the same speed as the horizontal speed component of the caterpillars 1. That is, the left and right caterpillars 1 are mutually tilted at a prescribed angle θ in the oblique upper right direction and rotated in the same rotational direction at an angular velocity ωwhile nipping the drawn part 100A of the optical fiber preform 100 therewith. Thereby, the drawn part 100A is subjected to drawing operations (drawing speed V=ω.cosθ) by the perpendicular component of the rotational speed ω.