A positioning device comprises a rotation mechanism and a clamping mechanism. The clamping mechanism is arranged on the rotation mechanism and used for clamping a workpiece. The rotation mechanism candrive the clamping mechanism and the workpiece to rotate. The rotation mechanism comprises an installing base, a drive assembly and a rotation table. The rotation table is rotationally arranged on the installing base. The drive assembly is arranged on the installing base so as to drive the rotation table to rotate relative to the installing base. Two abutting parts are arranged on the face, facing the installing base, of the rotation table in a spaced manner. The positioning device further comprises a stop block and a positioning assembly, the stop block is fixedly arranged on the face, facing the rotation table, of the installing base and is sandwiched between the two abutting parts, and the stop block can abut against the corresponding abutting part so as to stop rotation of the rotation table. A plurality of positioning holes are formed in the installing base at intervals. The positioning assembly comprises a positioning drive piece and positioning pins, the positioning pins penetrate the rotation table in a sliding manner, the positioning drive piece drives the positioning pins to move relative to the installing base, and accordingly the positioning pins can be arranged in thecorresponding positioning holes in a penetrating manner and position the rotation table.