A fat suction and graft syringe having a negative pressure adjustment means, the syringe having a plunger moving forward and rearward by being inserted into a barrel which is empty, and a needle coupled to a forward end of the barrel by a connector, wherein the syringe comprises: the negative pressure adjustment means supplying pressure allowing fat to be suctioned into the barrel by maintaining an inner space between a forward end of the plunger and the forward end of the barrel at a state of negative pressure during the rearward movement of the plunger, characterized in that the negative pressure adjustment means comprises: a multi-level holding plate formed in an inner space between partition walls of the plunger having a cross-shaped structure formed by the partition walls, the multi-level holding plate composed of at least one plate being formed perpendicularly to the partition walls and dividing the inner space between the partition walls into multi-level areas; and a single-surface rotation clip coupled to a side of an entrance of the barrel and having a bent part (322, 324) configured to be rotated only upward, i.e. rearward, and not to be rotated downward, i.e. forward, and hinged rotatably to a rotation clip fixing part, the rotation clip fixing part being open at a first side thereof and closed at a second side thereof, and configured to have a U shape such that the rotation clip fixing part is coupled to the barrel by fitting an inner space of the rotation clip fixing part over a finger support formed on an upper circumference of the barrel. the negative pressure adjustment means supplying pressure allowing fat to be suctioned into the barrel by maintaining an inner space between a forward end of the plunger and the forward end of the barrel at a state of negative pressure during the rearward movement of the plunger, characterized in that the negative pressure adjustment means comprises: a multi-level holding plate formed in an inner space between partition walls of the plunger having a cross-shaped structure formed by the partition walls, the multi-level holding plate composed of at least one plate being formed perpendicularly to the partition walls and dividing the inner space between the partition walls into multi-level areas; and a single-surface rotation clip coupled to a side of an entrance of the barrel and having a bent part (322, 324) configured to be rotated only upward, i.e. rearward, and not to be rotated downward, i.e. forward, and hinged rotatably to a rotation clip fixing part, the rotation clip fixing part being open at a first side thereof and closed at a second side thereof, and configured to have a U shape such that the rotation clip fixing part is coupled to the barrel by fitting an inner space of the rotation clip fixing part over a finger support formed on an upper circumference of the barrel. a multi-level holding plate formed in an inner space between partition walls of the plunger having a cross-shaped structure formed by the partition walls, the multi-level holding plate composed of at least one plate being formed perpendicularly to the partition walls and dividing the inner space between the partition walls into multi-level areas; and a single-surface rotation clip coupled to a side of an entrance of the barrel and having a bent part (322, 324) configured to be rotated only upward, i.e. rearward, and not to be rotated downward, i.e. forward, and hinged rotatably to a rotation clip fixing part, the rotation clip fixing part being open at a first side thereof and closed at a second side thereof, and configured to have a U shape such that the rotation clip fixing part is coupled to the barrel by fitting an inner space of the rotation clip fixing part over a finger support formed on an upper circumference of the barrel.