To produce an electrically conductive fiber having antistatic property to suppress static damage in low-humidity atmosphere and exhibiting heat- resistance and flexibility by forming a conductive layer composed of a specific conductive composition on the surface of a fiber.

An electrically conductive fiber holding a conductive layer and having a surface resistivity of 106 to 1012 Ω/(square) at 25°C and 15% RH, a charge attenuation time of ≤2 sec and a surface resistivity variation ratio of ≤5.0 after heating at 250°C for 1 min is produced by preparing an electrically conductive composition composed of a conductive polymer such as a polyaniline or its derivative, preferably a sulfonated polyaniline, e.g. aminoanisole sulfonic acid, a water-soluble or water-dispersible thermoplastic resin containing anionic group such as a copolymerized polyester containing 1-10 mol.% of a group selected from sulfonic acid group and its alkali metal salt group such as sodium 5-sulfoisophthalate unit and a surfactant and applying the conductive composition to the surface of fiber such as thread or sheet.