A flat belt (B) includes a cord retaining layer (11) in which a cord (14) extending in a belt length direction and arranged helically at a certain pitch in a belt width direction is embedded, and an inner rubber layer (12) provided on a belt inner side of the cord retaining layer (11) and serving as a pulley contracting portion. The cord retaining layer (11) is made of a rubber composition containing short fibers (15) which are mixed in a rubber component in an amount of 1 to 20 parts by mass relative to 100 parts by mass of the rubber component, and are dispersed to be oriented in the belt width direction. The inner rubber layer (12) is made of a rubber composition not containing short fibers (15).