[Problem] To suppress the growth of harmful bacteria without conducting heating treatment or adding an antiseptic agent and thereby provide noni juice which does not suffer from enzyme deactivation. [Solution] This process comprises subjecting noni juice, which has been obtained by squeezing harvested noni fruits, to preservation in an air-tight container at a temperature of 25 to 35ºC for a period of one week or longer. The process preferably comprises: preserving harvested noni fruits in a ripening vessel for a certain period and thereby ripening the noni fruits thereafter squeezing the ripened noni fruits to prepare noni juice having a pH of 3.6 to 3.8 preserving the noni juice in an air-tight container at a temperature of 25 to 35ºC for a period of one week or longer to prepare noni fruits having a pH of 3.5 or lower and thus obtaining noni juice which does not suffer from enzyme deactivation.
