METHOD FOR PRODUCING POLYACRYLONITRILE-BASED PRECURSOR FIBER, METHOD FOR PRODUCING CARBON FIBER, AND CARBON FIBER

PROBLEM TO BE SOLVED: To provide carbon fibers having high tensile modulus and compressive strength and to provide a method for producing the carbon fibers without deteriorating productivity and processability, and to further provide a method for producing polyacrylonitrile-based precursor fibers for producing the carbon fibers used for producing the carbon fibers. SOLUTION: The method for producing the polyacrylonitrile-based precursor fibers includes a spinning step of discharging from a spinneret by a wet spinning method or a dry-jet wet spinning method, a water-washing step of washing the fibers obtained in the spinning step in a water bath, a water-bath drawing step of drawing the fibers obtained in the water-washing step in water baths, a dry heat-treating step of dry heat-treating the fibers obtained in the water-bath drawing step and a steam drawing step of steam drawing the fibers obtained in the dry heat-treating step. In the method for producing the polyacrylonitrile-based precursor fibers, a spinning solution contains a polyacrylonitrile-based polymer having an intrinsic viscosity within the range of 2.0-10 and a concentration of the polyacrylonitrile-based polymer of ≥10 to