Production method for separated fiber bundle, separated fiber bundle, fiber-reinforced resin molding material using separated fiber bundle, and production method for fiber-reinforced resin molding material using separated fiber bundle

A method of producing a separated fiber bundle, comprising at least steps [A] and [B] are performed in this order:

• [A] a partial separation step of obtaining a partially separated fiber bundle in which separation-processed parts, each separated into a plurality of completely divided fiber bundles, and not-separation-processed parts are alternately formed along the lengthwise direction of a fiber bundle comprising a plurality of single fibers;
• and
• [B] a cutting step of cutting the not-separation-processed parts of the partially separated fiber bundle formed in the step [A] along the lengthwise direction of the fiber bundle,
• wherein, in the step [B], after performing a widening processing to the partially separated fiber bundle, the not-separated-processed part is cut along the lengthwise direction of the fiber bundle.