A power transmission belt at least includes a bottom rubber layer. A rubber composition for forming the bottom rubber layer contains a rubber component, cellulose fine fibers, and short fibers. The cellulose fine fibers have an average diameter from 1 nm to 200 nm, and the rubber composition contains 0.5 parts by mass or more of the cellulose fine fibers relative to 100 parts by mass of the rubber component. The short fibers have an average diameter from 5 μm to 30 μm, and the rubber composition contains 1 part by mass or more of the short fibers relative to 100 parts by mass the rubber component.