An optical fiber base material manufacturing method for sequentially depositing glass particles on a tip of a starting material drawn up at a drawing up speed while being rotated in a VAD method, the optical fiber base material manufacturing method comprising: supplying oxygen, hydrogen, and silicon tetrachloride to a core deposition burner and a cladding deposition burner, the supplied hydrogen being switched between normal hydrogen, in which orthohydrogen and parahydorogen are in an equilibrium state at normal temperature, and hydrogen obtained by vaporizing liquid hydrogen and having a higher ratio of parahydrogen to orthohydrogen than the normal hydrogen; sequentially depositing, on the tip of the starting material, silicon dioxide generated in an oxyhydrogen flame by means of hydrolysis to grow a porous base material; adjusting the drawing up speed so that a tip position of the deposition remains at the same position in accordance with growth of the porous base material; calculating an average of the drawing up speed at a preset time interval; calculating a difference between the calculated average and a preset value of the drawing up speed; correcting a flow rate of silicon tetrachloride supplied to the core deposition burner depending on the difference when the supplied hydrogen is the normal hydrogen, and correcting a flow rate of hydrogen supplied to the core deposition burner depending on the difference when the supplied hydrogen is the hydrogen obtained by vaporizing liquid hydrogen, wherein when correcting the flow rate of hydrogen, a flow rate of hydrogen supplied to the cladding deposition burner is also corrected in a ratio that is the same as a ratio of before and after the correction of the flow rate of the hydrogen supplied to the core deposition burner, and the flow rate of the hydrogen supplied to the core deposition burner and the cladding deposition burner is controlled by a mass flow controller whose measurement principle is based on thermal capacity measurement of gas. supplying oxygen, hydrogen, and silicon tetrachloride to a core deposition burner and a cladding deposition burner, the supplied hydrogen being switched between normal hydrogen, in which orthohydrogen and parahydorogen are in an equilibrium state at normal temperature, and hydrogen obtained by vaporizing liquid hydrogen and having a higher ratio of parahydrogen to orthohydrogen than the normal hydrogen; sequentially depositing, on the tip of the starting material, silicon dioxide generated in an oxyhydrogen flame by means of hydrolysis to grow a porous base material; adjusting the drawing up speed so that a tip position of the deposition remains at the same position in accordance with growth of the porous base material; calculating an average of the drawing up speed at a preset time interval; calculating a difference between the calculated average and a preset value of the drawing up speed; correcting a flow rate of silicon tetrachloride supplied to the core deposition burner depending on the difference when the supplied hydrogen is the normal hydrogen, and correcting a flow rate of hydrogen supplied to the core deposition burner depending on the difference when the supplied hydrogen is the hydrogen obtained by vaporizing liquid hydrogen, wherein when correcting the flow rate of hydrogen, a flow rate of hydrogen supplied to the cladding deposition burner is also corrected in a ratio that is the same as a ratio of before and after the correction of the flow rate of the hydrogen supplied to the core deposition burner, and the flow rate of the hydrogen supplied to the core deposition burner and the cladding deposition burner is controlled by a mass flow controller whose measurement principle is based on thermal capacity measurement of gas.