A method of fixing a workpiece on a table of a machine tool using a workpiece fixing jig, characterized in that: the workpiece fixing jig comprises a base to be fixed on the table, and a clamping mechanism provided on the base for clamping the workpiece, the clamping mechanism including a first clamping portion and a second clamping portion provided to face each other, at least one of the first and second clamping portions (20, 30) being configured to move forward and backward with respect to the other along a moving direction, and the moving direction intersecting a direction of fixation of the base to the table; the first clamping portion is composed of a screw shaft; the clamping mechanism includes: a first block having a through hole formed therein and holding the first clamping portion in the through hole, the through hole being formed along the moving direction and having a large diameter on a side closer to the second clamping portion and a small diameter on a side opposite thereto; a second block holding the second clamping portion; a biasing body inserted in a deep side of the large diameter side of the through hole of the first block; and a nut inserted in an open side of the large diameter side of the through hole in a non-rotatable manner; the first clamping portion is screwed in the nut in a state of passing through the biasing body and has a distal end protruding toward the second clamping portion; the workpiece has a plurality of clamped portions (Wa) formed on the side surfaces thereof, each of the clamped portions (Wa) having a rectangular parallelepiped shape; and the method comprises: placing the workpiece on the table; thereafter, by using a plurality of said workpiece fixing jigs, respectively clamping each of the clamped portions (Wa) of the workpiece by the first clamping portion and the second clamping portion by means of a resilient force of the biasing body between the first clamping portion and the second clamping portion of each of the workpiece fixing jigs; and thereafter, fixing the base of each of the workpiece fixing jigs onto the table. the workpiece fixing jig comprises a base to be fixed on the table, and a clamping mechanism provided on the base for clamping the workpiece, the clamping mechanism including a first clamping portion and a second clamping portion provided to face each other, at least one of the first and second clamping portions (20, 30) being configured to move forward and backward with respect to the other along a moving direction, and the moving direction intersecting a direction of fixation of the base to the table; the first clamping portion is composed of a screw shaft; the clamping mechanism includes: a first block having a through hole formed therein and holding the first clamping portion in the through hole, the through hole being formed along the moving direction and having a large diameter on a side closer to the second clamping portion and a small diameter on a side opposite thereto; a second block holding the second clamping portion; a biasing body inserted in a deep side of the large diameter side of the through hole of the first block; and a nut inserted in an open side of the large diameter side of the through hole in a non-rotatable manner; a first block having a through hole formed therein and holding the first clamping portion in the through hole, the through hole being formed along the moving direction and having a large diameter on a side closer to the second clamping portion and a small diameter on a side opposite thereto; a second block holding the second clamping portion; a biasing body inserted in a deep side of the large diameter side of the through hole of the first block; and a nut inserted in an open side of the large diameter side of the through hole in a non-rotatable manner; the first clamping portion is screwed in the nut in a state of passing through the biasing body and has a distal end protruding toward the second clamping portion; the workpiece has a plurality of clamped portions (Wa) formed on the side surfaces thereof, each of the clamped portions (Wa) having a rectangular parallelepiped shape; and the method comprises: placing the workpiece on the table; thereafter, by using a plurality of said workpiece fixing jigs, respectively clamping each of the clamped portions (Wa) of the workpiece by the first clamping portion and the second clamping portion by means of a resilient force of the biasing body between the first clamping portion and the second clamping portion of each of the workpiece fixing jigs; and thereafter, fixing the base of each of the workpiece fixing jigs onto the table. placing the workpiece on the table; thereafter, by using a plurality of said workpiece fixing jigs, respectively clamping each of the clamped portions (Wa) of the workpiece by the first clamping portion and the second clamping portion by means of a resilient force of the biasing body between the first clamping portion and the second clamping portion of each of the workpiece fixing jigs; and thereafter, fixing the base of each of the workpiece fixing jigs onto the table.