Partially separated fiber bundle and method of manufacturing same

A method of manufacturing a partially separated fiber bundle comprising allowing a fiber bundle that contains a plurality of single yarns to travel in a longitudinal direction and to be widened, and intermittently sticking a fiber separating device into a widened fiber bundle to form a separated fiber section and an unseparated fiber section in the fiber bundle,

• wherein a sizing agent is applied to the widened fiber bundle between a fiber bundle widening step and a fiber separation step, the sizing agent being a water-soluble polyamide resin, and
• the fiber separating device is stuck at a plurality of points in a width direction of the fiber bundle while being shifted in the longitudinal direction to adjust Amin (units/mm) to 0.5 units/mm or larger and to adjust a ratio Amax/Amin to 1.1 or larger and 3 or smaller when the number of fiber bundles contained in the width direction of the partially separated fiber bundle (fiber separating number:
• Nn (units)) measured at a freely selected point Pn, wherein n represents an integer of 1 to 100, and freely selected points Pn and Pn+1, excluding n=100, being 50 cm or more away from each other, is divided by a full width of Wn (mm) of the partially separated fiber bundle, to determine the fiber separating number per unit width An (units/mm), and assuming its maximum value as Amax (units/mm) and its minimum value as Amin (units/mm).