The present invention provides a method of manufacturing a mixed beverage that offers an excellent flavor and superior preservation stability, and that contains vegetable juice etc. and soybean protein, and a mixed beverage that can be obtained by the manufacturing method. The method of the present invention for manufacturing a mixed beverage includes the following steps. (1) A first step for treating vegetable juice and/or fruit juice with pectin lyase, and then deactivating the pectin lyase. (2) A second step for pH adjusting the pectin lyase treated liquid obtained in the first step so that the final pH of the mixed beverage becomes 3.0 to 4.5. (3) A third step for adding low phytate soybean protein to the pH-adjusted liquid obtained in the second step.