Abstract: A fibroin fluid obtained by adding carbon dioxide to a fibroin aqueous solution and then completely removing the carbon dioxide by pressure reduction or heating has fibroin microstructures which are dispersed in a dispersing medium, the fibroin fluid, unlike a conventional fibroin gel, having a fluidity sufficient for bringing it into the sate of a cream, having the property of excellent humidity retention and being widely usable as an agent for decreasing cholesterol or cosmetic.