The invention discloses a double roller drafting device. After passing through a rear nip from a bell mouth, a roving yarn (8) is absorbed onto a grid ring by negative pressure air current. When the roving yarn (8) attached on the grid ring (9) moves forward, the outwardly-expanded long fibers are concentrated around the roving yarn (8) by the negative pressure air current. With the forward movement of the grid ring(9), the roving yarn (8) passes through an elastic nip formed by a rear pressure bar (4) and the grid ring (9) to a front nip and is drafted by the front nip. Since the front pressure bar (2) presses the floating area of fiber strands, the quality of obtained yarns is good in evenness and less in hairiness.