The invention discloses a centering device used during guide rail conveying. The centering device comprises a fixed base, a first swing arm, a second swing arm, a telescopic drive device and guide rollers; the rear end of the first swing arm and the rear end of the second swing arm are each provided with a first rotating shaft pointing to the fixed base downwards, and are each provided with a second rotating shaft pointing to the upper portion, the guide rollers are arranged on the second rotating shafts, and the first rotating shafts are correspondingly sleeved with gears; and through the manner, according to the centering device used during guide rail conveying, the telescopic drive device carries out telescopic operation to drive the first swing arm or the second swing arm to swing, meanwhile, the first swing arm and the second swing arm are engaged through the gears to synchronously move, the included angle between the first swing arm and the second swing arm is changed, the distance between the two guide rollers is changed also, the centering device is suitable for guide rails of different widths, before the guide rails are centered, the distance between two guide rollers is increased, and impact of the guide rails is avoided.