Provided is a short rubber reinforcement fiber for short fiber-containing rubber compositions that are used for transmission belts for which friction transmission behavior has been stabilized and travel service life has been further improved. The present invention is a short fiber, which is the product of cutting an adhesive-treated synthetic long fiber multifilament yarn and is used by dispersing in a rubber composition, the short fiber being characterized in that the percentage of the number of non-adhesive-treated single yarns is 0-5%; and a method for manufacturing said short fibers, the method comprising a step for immersing a sudare-woven product in which the synthetic long fiber multifilament yarns have been sudare-woven in an adhesive treatment solution and then pressing at a nip pressure of 1.2-5.0 MPa using nip rolls, and a step for cutting the sudare-woven product bundles obtained to a specified length.