The present invention relates to a screw assembly for a spinal implant comprising a first unit including insertion holes positioned opposite each other, cut from an edge of an upper end of the first unit, and forming an inner space, the first unit penetrated from top to bottom, a rod having a side whose outer circumference surface is positioned on the insertion holes of the first unit and another side whose outer circumference surface is positioned on an insertion holes of another first unit positioned adjacent to the first unit, a second unit having an upper portion rotatably received in a lower portion of the inner space and a lower portion screwed to a vertebral body of a spine not to be released； a third unit screwed to an upper portion of the inner space to hold the rod, and a fourth unit positioned between the inner space and the upper portion of the second unit to restrict a rotation of the second unit and including a pressure cap seated in the inner space while pressing an outer surface of an upper portion of a hall joint head disposed on the upper portion of the second unit and having an upper portion contacting the outer circumference surface of the rod to be pressurized by a coupling force of the third unit coupled with the first unit.
