A grease filter comprising: a first plate; a second plate arranged on the first plate; a third plate arranged to face the second plate; a fourth plate arranged on the third plate; the first plate and the second plate having overlapping inlet portions through which an air current flows in, and wherein each of the first plate and the second plate comprise a plurality of first guide units (110, 110a, 110b) protruding towards the third plate and the fourth plate, the first guide units (110, 110a, 110b) configured to guide the air current flowing in through the inlet portions; the third plate and the fourth plate having overlapping outlet portions through which the air current flowing in through the inlet portions is discharged to the outside, and wherein each of the third plate and the fourth plate comprise a plurality of second guide units (210, 210a, 210b) protruding towards the first plate and the second plate, the second guide units (210, 210a, 210b) configured to guide the air current to discharge the air current through the outlet portions, wherein the plurality of first guide units (110, 110a, 110b) each comprise: an inlet guide inclined obliquely from the first plate and the second plate toward the third plate and the fourth plate; and a first direction change guide curved from the inlet guide, and the plurality of second guide units (210, 210a, 210b) each comprise: an outlet guide inclined obliquely from the third plate and the fourth plate toward the first plate and the second plate; and a second direction change guide curved from the outlet guide; wherein the first (110, 110a, 110b) and second (210, 210a, 210b) guide units cross each other and together form a direction change path and a guide path for guiding the air current in the filter from the same inlet portion to different outlet portions and for filtering oil particles by colliding with the air current, wherein the direction change path spans between the first direction change guide and the second direction change guide and is configured to change the direction of the air current flowing in through the inlet portion to interrupt the flow of the air current, and the guide path is formed between the first guide unit (110, 110a, 110b) and the second guide unit (210, 210a, 210b) and is configured to bypass the first direction change guide and the second direction change guide and configured to have a longer path length than the direction change path, and wherein the first plate and the second plate are detachable from the third plate and the fourth plate. a first plate; a second plate arranged on the first plate; a third plate arranged to face the second plate; a fourth plate arranged on the third plate; the first plate and the second plate having overlapping inlet portions through which an air current flows in, and wherein each of the first plate and the second plate comprise a plurality of first guide units (110, 110a, 110b) protruding towards the third plate and the fourth plate, the first guide units (110, 110a, 110b) configured to guide the air current flowing in through the inlet portions; the third plate and the fourth plate having overlapping outlet portions through which the air current flowing in through the inlet portions is discharged to the outside, and wherein each of the third plate and the fourth plate comprise a plurality of second guide units (210, 210a, 210b) protruding towards the first plate and the second plate, the second guide units (210, 210a, 210b) configured to guide the air current to discharge the air current through the outlet portions, wherein the plurality of first guide units (110, 110a, 110b) each comprise: an inlet guide inclined obliquely from the first plate and the second plate toward the third plate and the fourth plate; and a first direction change guide curved from the inlet guide, and an inlet guide inclined obliquely from the first plate and the second plate toward the third plate and the fourth plate; and a first direction change guide curved from the inlet guide, and the plurality of second guide units (210, 210a, 210b) each comprise: an outlet guide inclined obliquely from the third plate and the fourth plate toward the first plate and the second plate; and a second direction change guide curved from the outlet guide; an outlet guide inclined obliquely from the third plate and the fourth plate toward the first plate and the second plate; and a second direction change guide curved from the outlet guide; wherein the first (110, 110a, 110b) and second (210, 210a, 210b) guide units cross each other and together form a direction change path and a guide path for guiding the air current in the filter from the same inlet portion to different outlet portions and for filtering oil particles by colliding with the air current, wherein the direction change path spans between the first direction change guide and the second direction change guide and is configured to change the direction of the air current flowing in through the inlet portion to interrupt the flow of the air current, and the guide path is formed between the first guide unit (110, 110a, 110b) and the second guide unit (210, 210a, 210b) and is configured to bypass the first direction change guide and the second direction change guide and configured to have a longer path length than the direction change path, and wherein the first plate and the second plate are detachable from the third plate and the fourth plate.