PURPOSE: To obtain a polybenzazole fiber hardly having denier unevenness in the longitudinal direction, excellent in uniformity and having high strength and modulus by subjecting polybenzazole dope to dry wet spinning through a specific spinneret.

CONSTITUTION: A polybenzazole polymer solution polymerized in a polyphosphoric acid solvent is directly used as a spinning dope and kneaded and subjected to defoaming treatment in a two-axle kneader and fed to a spinning head and spinning fine holes radially extended from the center of a spinneret are divided and perforated by a dividing zone 3 which is not perforated and discharged through spinneret having ≥2.0/cm2 and <5.0/cm2 hole density of a spinning hole group 2 to form dope filaments to form dope filament and successively actively cooled in stream kept to 30-100°C in an air gap and brought into contact with a solvent-insoluble coagulating bath of a phosphoric acid water solution and taken off to provide the objective polybenzazole fiber having relatively fine single yarn at high spinning rate of ≥200m/min in good productivity.