Abstract: An intramedullary nail fixation apparatus and its fixation method, the apparatus including a tubular intramedullary nail having a plurality of equiangularly spaced piercing points, and a plurality of flexible screws respectively mounted in the intramedullary nail and forced to fix the intramedullary nail to the marrow cavity of the bone to be fixed, each flexible screw having a rounded stem convenient for rotation, and a self-tapping screw tip at one end of the rounded stem convenient for being forced out of the intramedullary nail through one piercing point and then threaded into the wall of the bone upon rotation of the respective flexible screw. The invention relates also to the method of the fixation of the apparatus.