There is provided an elongation method of an optical fiber base material, by which a base material rod not requiring a process for modifying a bend from base material ingot is obtained. The method for elongating base material ingot to be a base material rod having a diameter smaller than before to manufacture an optical fiber base material, includes the steps of: elongating the base material ingot while controlling a control position so that a neck-down within a horizontal surface of the base material ingot is located at a target position; measuring a bending direction and a bending amount of an elongated base material rod; and adjusting the target position based on the result. In addition, it is preferable to adjust a position of a pendant portion of base material ingot in order to control the position of the neck-down to be the target position. For example, the position of the pendant portion may be moved in an XY direction, more particularly, in a direction in which the measured bend shows convexity.