To provide a synthetic fiber dyeable to a color similar to natural fiber with a common natural dye and giving a natural placid color of a natural dye.

This dyed synthetic fiber is produced by fixing a natural protein to the surface of a synthetic fiber and dyeing the natural protein with a natural dye. The synthetic fiber is preferably a polyester fiber and the natural protein is preferably insolubilized by crosslinking or fixed with a binder. The natural protein is preferably mordanted with a mordant, preferably a metal compound mordant.