The invention relates to a turning device for a U-shaped beam, comprising a plurality of turning mechanisms arranged at intervals, wherein a rotating shaft base and a slideway base of each turning mechanism are respectively and horizontally connected to the top end of an upright post; the upright post is connected to a support seat; a slideway is perpendicular to a rotating shaft and is supportedon the slideway base; the center of the slideway is positioned under the rotating shaft; a guiding seat is also arranged on the slideway base; a guiding shaft is inserted to the guiding seat; the axis of the guiding shaft is in parallel to the slideway; a pulling plate is arranged at one end of the guiding shaft; a pushing plate is arranged at the other end of the guiding shaft; the rotating shaft is arranged on the rotating shaft base through a bearing block and is fixedly connected with a turner; the turner is provided with a U-shaped clamping groove matched with the U-shaped beam; the center line of the U-shaped clamping groove is in parallel to the top surface of the slideway; the height of the U-shaped clamping groove, the pulling plate and the height of the pushing plate are matchedwith height of the U-shaped beam arranged on the slideway; and the rotating shaft of each turning mechanism is coaxially connected by using a coupling. The tuning device can be used for easily turning the U-shaped beam by 180 degrees and is time-saving, labor-saving, safe and reliable.