A blowing control method for a converter type dephosphorization refining furnace, the method comprising: an in-furnace oxygen accumulation amount calculating step of calculating an amount of oxygen accumulated in a furnace, based on blowing conditions including a feed amount of oxygen and a charging amount of auxiliary material for a converter type dephosphorization refining furnace, measurement results of the converter type dephosphorization refining furnace including a flow rate and a component concentration of exhaust gas in the converter type dephosphorization refining furnace, and analytical values of components and a temperature of molten iron; a feature point extracting step of sequentially monitoring a change of the amount of oxygen accumulated in the furnace during a blowing treatment and extracting a feature point of fluctuations in the amount of oxygen accumulated in the furnace; a blow end oxygen amount determining step of determining an amount of oxygen at blow end until the blowing treatment is completed, based on the feature point extracted at the feature point extracting step; and a control step of completing the blowing treatment at a timing at which the accumulated feed amount of oxygen fed into the converter type dephosphorization refining furnace has reached the amount of oxygen at blow end determined at the blow end oxygen amount determining step, wherein the feature point extracting step includes a step of extracting, as a feature point, a point at which a rate of increase in the amount of oxygen accumulated in the furnace is equal to or less than zero. an in-furnace oxygen accumulation amount calculating step of calculating an amount of oxygen accumulated in a furnace, based on blowing conditions including a feed amount of oxygen and a charging amount of auxiliary material for a converter type dephosphorization refining furnace, measurement results of the converter type dephosphorization refining furnace including a flow rate and a component concentration of exhaust gas in the converter type dephosphorization refining furnace, and analytical values of components and a temperature of molten iron; blowing conditions including a feed amount of oxygen and a charging amount of auxiliary material for a converter type dephosphorization refining furnace, measurement results of the converter type dephosphorization refining furnace including a flow rate and a component concentration of exhaust gas in the converter type dephosphorization refining furnace, and analytical values of components and a temperature of molten iron; a feature point extracting step of sequentially monitoring a change of the amount of oxygen accumulated in the furnace during a blowing treatment and extracting a feature point of fluctuations in the amount of oxygen accumulated in the furnace; sequentially monitoring a change of the amount of oxygen accumulated in the furnace during a blowing treatment and extracting a feature point of fluctuations in the amount of oxygen accumulated in the furnace; a blow end oxygen amount determining step of determining an amount of oxygen at blow end until the blowing treatment is completed, based on the feature point extracted at the feature point extracting step; and a control step of completing the blowing treatment at a timing at which the accumulated feed amount of oxygen fed into the converter type dephosphorization refining furnace has reached the amount of oxygen at blow end determined at the blow end oxygen amount determining step, wherein the feature point extracting step includes a step of extracting, as a feature point, a point at which a rate of increase in the amount of oxygen accumulated in the furnace is equal to or less than zero. <EOS>