PURPOSE: To provide a Ca treatment method of molten steel.

CONSTITUTION: A carrier gas blowing speed V is controlled in compliance with the following equation (1) according to the adding speed of a Ca-contg. material at the time of blowing the Ca-contg. material by using a carrier gas into the molten steel 2 in a ladle previously subjected to a deoxidation treatment: (5.6×C+1.5)≤V≤(46.4×C+5.23)...(1), where C: the adding speed of the Ca-contg. material, [kg/(T.min)]; V: the blowing speed of the carrier gas, [Nl/(T×min)]. As a result, the yield of Ca is stabilized, harmful inclusions are reformed and cleanliness is improved. This method is adequate for producing steel products having extremely high HIC resistance.