Abstract: A six-degree-of-freedom parallel mechanism is provided for expanding a grade of a spindle. The parallel mechanism has a spindle that turns round a workpiece at a tilting angle of 90.degree. in a workspace, to thereby allow a machining for both vertical and horizontal planes of the workpiece, and a vertical turning process, by a single machining center. A six-axis multi-machining type machining center embodying the parallel mechanism of the present invention is also disclosed. An over-actuated multi-machining type machining center further including over-actuated actuators is presented to solve a problem of driving joints' singularity caused by the parallel mechanism.