A textured protein comprising as main ingredients soybean protein, casein and water, and a frozen processed food in which the textured protein is mixed are disclosed. The textured protein is produced by heating a mixture of soybean protein, casein and water under pressure, followed by extruding the mixture to the atmosphere to expand. The textured protein has function to give a juicy texture of a freshly cooked food to the frozen processed food, even if the food is re-heated upon eating after being frozen and distributed to the market.