Provided is a texture-improving agent for a starch processed food, which exhibits an effect of improving texture by being added to a starch processed food. By using a physical property-improving agent containing, as an active ingredient, a separated soybean protein composition obtained by drying in the form of an acid precipitate, a starch processed food having improved physical properties can be obtained. More specifically, the agent has an effect of improving physical properties and texture, for example, enhancing physical strength such as chewiness and elasticity, improving crispness and stickiness, and so on, and also has an effect of maintaining the improved properties and texture.