A test device of universal nail/screw holding power is provided. The device is capable of penetrating a nail/screw into a test piece at any angle and positioning the test piece on which a nail/screw is penetrated at any angle to test the nail/screw holding power. The device includes a base, two opposite supporting plates, two coaxial disks, an upper bearing plate, a lower bearing plate, a side bearing plate, a through groove, a trapezoid slot, and a plurality of trapezoid bolts on the same circumference. When the disk is turned, at least one trapezoid bolt is inserted into the trapezoid slot; when the at least one trapezoid bolt engages with the trapezoid slot and then is tightened up, the at least one trapezoid bolt and the trapezoid slot cooperatively limit the turn of the disk.