Abstract: A method of preparing a fermented soybean milk comprising subjecting a soybean milk to fermentations with yeast and lactic acid bacteria, and subjecting the resulting fermented soybean milk to a deactivation treatment to deactivate the yeast and bacteria by heating and a removal treatment to remove alcohol and carbon dioxide gas contained therein. As a result, a fermented soybean milk which is a beverage suiting everybody's taste, and a packed product thereof which is not subject to expansion or deformation during storage, are obtained.