To provide a powdery soybean protein capable of imparting favorable water holding properties and hardness to a processed product of livestock meat such as a ham.

This powdery soybean protein has pH 8.0-10.0 of a 5% aqueous solution thereof. An additive for the processed product of the livestock meat comprises the powdery soybean protein. The method for producing the processed product of the livestock meat comprising the powdery soybean protein is provided. An organic acid salt may be contained in the powdery soybean protein. Effects are further enhanced by using a transglutaminase when the processed product of the livestock meat is produced. The processed product of the livestock meat having improved quality such as the water holding properties and product strength is obtained by using the powdery soybean protein. Functions thereof are equal to those of polyphosphates.