A method for identifying barley with good brewing properties using the thermostability of the barley β-amylase as an indicator. The thermostability of the barley β-amylase significantly affects the degree of the apparent attenuation limit. A method for determining the enzyme activity of an extract solution from one barley seed, an indirect method by an isoelectric point, and an indirect identifying method by DNA polymorphisms of the region containing the β-amylase structural gene have been developed as a method for determining the type of thermostability for a barley β-amylase. The selection method is not affected by environmental or climatic conditions.