To provide a functional fiber giving little harmful influence on the human body and environment in all stages of the production, use and disposal, having the adhesiveness of a modified polyolefin and improved safety and exhibiting excellent flame retardance by the addition of a small amount of a flame retardant and provide a formed fiber material produced by using the functional fiber.

The functional fiber contains a modified polyolefin graft-polymerized with at least one kind of vinyl monomer (modifier) selected from unsaturated carboxylic acids and unsaturated carboxylic acid anhydrides and a nitrogen-containing phosphorus compound.