▎ 摘　　要

NOVELTY - Pitch-based carbon fiber of which the defect number density is 40/m or less and the shape of the cross-section perpendicular to the longitudinal direction is circular or elliptical with 0.25 oblateness or less, and which has a boundary surface in the diametrical direction of the circular cross-section or in the longitudinal direction of the elliptical cross-section. USE - The pitch-based carbon fiber is used for a fiber-reinforced plastic (claimed). ADVANTAGE - The pitch-based carbon fiber has excellent tensile strength. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for producing a pitch-based carbon fiber, including a melt spinning process in which molten anisotropic pitch is discharged from a spinning nozzle and spun, where the ratio of the length of the long side of the circumscribing rectangle circumscribing the shape of the ejection hole of the spinning nozzle is greater than 1 to the length of the short side of the circumscribing rectangle, and the melted anisotropic pitch has a viscosity of 20-80 Pa.second.