PURPOSE: To provide a Ca treating method in molten steel.

CONSTITUTION: In the Ca treating method adding Ca-containing material and simultaneously, flux consisting essentially of CaO-Al2O3 into the deoxidized molten steel in a ladle, this treating method is to satisfy the following inequality (1) on CaO/Al2O3 wt. ratio in the flux and the following inequality (2) on the adding quantity of the flux: -0.016×(%Ca)+1.6>(CaO/Al2O3)>-0.0044×(% Ca)+0.44...(1). 0.8>[flux]/[Ca]>0.3... (2). Wherein, (%Ca) is Ca% in the Ca- containing material, [flux] is added quantity of the flux (kg/T) and [Ca] is adding quantity of the converted pure Ca (kg/T). By this method, the development of harmful inclusion of CaS, MnS and Al2O3 cluster, etc., is restrained and also, the high m.p. composition CaO-Al2O3 base inclusion is refomed to the low m.p. composition and the steel material excellent in HIC resistance can be produced.