A workpiece turning-over device includes a mounting wall, a gear driving mechanism, and a rotation mechanism. The gear driving mechanism comprises a toothed bar and a driving member. The driving member is able to drive the toothed bar to move. The rotation mechanism comprises a sleeve and a gear. The sleeve is rotatably attached to the mounting wall. A supporting portion extends from the sleeve to secure the workpiece thereon. The gear is fixedly coiled around the sleeve, engaged to the toothed bar, and is able to rotate to rotate the sleeve fixed thereto, thereby allowing the workpiece to rotate.