This invention provides a novel solubilized collagen fiber capable of being uniformly solved in water instantly to obtain solubilized collagen when used. The solubilized collagen fiber is consisted of solubilized collagen solid contents of 66 to 87% by weight, a buffer salt of 2 to 6% by weight, water content of 10 to 22% by weight, and residual hydrophilic organic solvent present in an amount of tracer level to 6% by weight (the above components are 100% by weight in total), wherein the average fineness of the solubilized collagen fiber is 3 to 10dtx, the isoionic point of the solubilized collagen fiber is 4.5 to 5.0, and the water content of 10 to 22% by weight as well as the residual hydrophilic organic solvent present in an amount of tracer level to 6% by weight are present uniformly in a length direction of the fiber. The buffer salt is selected from sodium citrate, sodium citrate, and sodium phosphate.
