It is intended to provide a milk drink obtained by starting with a milk protein-containing powder (skim milk powder, etc.) having a seriously worsened flavor which is free from worsening in the flavor after heating and sustains a flavor comparable to a product obtained by starting with fresh milk or fermented milk alone without using such a starting material as described above. An inert gas such as nitrogen gas is bubbled into a conditioned milk liquor containing a milk protein-containing powder (for example, whole milk powder or defatted milk powder) which is obtained by starting with fresh milk or milk so as to lower the dissolved oxygen concentration in the conditioned milk liquor to 8 ppm or below. Next, the conditioned milk liquor is subjected as such to heat sterilization.