An object of the present invention is to provide a fiber that is excellent in safety, can be easily produced, and has resistance to organic solvents, a raw material composition for producing the fiber, and a biocompatible material containing the fiber. (A) A fiber produced by spinning a composition containing a condensation product obtained by condensing one or more of the compounds represented by formula (1) and (B) an acid compound. [Each symbol in the formula is as described in the specification. ]
