<p>A fiber is provided which is made only of a polymer having crystallinity and has voids in inner parts thereof. Also provided is a process for producing the fiber. The process for fiber production includes: a melt spinning step in which a resin composition comprising a polymer having crystallinity as the only polymer ingredient is melt-spun; and a stretching step in which stretching is conducted at a speed of 10-2,000 m/min and at a stretching temperature (T, °C) satisfying the relationship represented by (Tg-30)=T=(Tg+50), wherein T (°C) is the stretching temperature and Tg (°C) is the glass transition temperature of the polymer having crystallinity.</p>
