To provide a method for reducing the concentration of sodium in a plum vinegar or a desalinized plum juice, and further to provide a method for producing a plum juice drink having decreased sodium concentration and increased potassium concentration from the plum juice using the plum vinegar as a starting raw material.

A strong acid is added to a plum juice in a desalinizing treatment or the plum juice after desalinization, and the plum juice with the strong acid is treated with an ion-exchange membrane electrodialysis. A potassium source is added to the obtained plum juice with a reduced sodium concentration in the method for producing the plum juice drink.