MOISTURE-ABSORBING OR RELEASING SYNTHETIC FIBER

PROBLEM TO BE SOLVED: To provide a moisture-absorbing or releasing synthetic fiber having an excellent moisture-absorbing or releasing performance capable of exhibiting a moisture-absorbing function or a moisture-releasing function in response to the temperature and humidity states of an environment and capable of repeatedly exhibiting the moisture-absorbing or releasing performance, even when the states of temperature and humidity are changed, extremely scarcely changing the color tone of the fiber, especially yellowing the color, even when stored for a long period, and not having a problem on the touch and dyeability of clothing, even when used for the use of the clothing. SOLUTION: This synthetic fiber comprises a moisture-absorbing or releasing component and a fiber-forming polymer, and has a moisture-absorbing property of >=1.5%, when the synthetic fiber reached an equilibrium moisture content under an environment of 25 deg.C×60% RH is left under an environment of 34 deg.C×90% RH for 30 min, and a moisture-releasing property of ":;z2%, when the synthetic fiber reached an equilibrium moisture content under an environment of 34 deg.C×90% RH is left under an environment of 25 deg.C×60% RH for 30 min. The synthetic fiber has a (b) value of -1 to 5 in the CIE-LAB color system, when left for 30 days.