An active material coating apparatus comprising: a lower die having a groove for supplying an active material in a slurry state, wherein the lower die forms a first lip portion of an outlet slot connected to the groove which outputs the active material; an upper die disposed on an upper side of the lower die to face the first lip portion and assembled on the lower die, wherein the upper die comprises a second lip portion of the outlet slot, a hinge portion at the rear of the second lip portion according to the outlet direction of the active material, and an adjusting screw that is screw-coupled to the hinge portion, wherein the adjusting screw is configured to be controlled in a clockwise direction or an anti-clockwise direction; a fixing spacer having a first thickness interposed between the lower die and the upper die at the rear of the hinge portion according to the outlet direction of the active material, wherein the fixing spacer determines a fixing gap (Gi); a flexible spacer having a second thickness interposed between the first lip portion and the second lip portion on both sides of the width direction of the outlet slot and forming a variable gap, wherein the flexible spacer is supported by an end of the fixing spacer, is movable so as to adjust the width of the outlet slot, and is configured such that rotation of the adjusting screw moves the second lip portion in the z-axis direction with respect to the first lip portion, such that a position of the y-axis direction of the flexible spacer between the first lip portion and the second lip portion is controlled; and a controller installed on the upper die and arranged to move the second lip portion with respect to the hinge portion to control the variable gap between the first lip portion and the second lip portion. a lower die having a groove for supplying an active material in a slurry state, wherein the lower die forms a first lip portion of an outlet slot connected to the groove which outputs the active material; an upper die disposed on an upper side of the lower die to face the first lip portion and assembled on the lower die, wherein the upper die comprises a second lip portion of the outlet slot, a hinge portion at the rear of the second lip portion according to the outlet direction of the active material, and an adjusting screw that is screw-coupled to the hinge portion, wherein the adjusting screw is configured to be controlled in a clockwise direction or an anti-clockwise direction; a fixing spacer having a first thickness interposed between the lower die and the upper die at the rear of the hinge portion according to the outlet direction of the active material, wherein the fixing spacer determines a fixing gap (Gi); a flexible spacer having a second thickness interposed between the first lip portion and the second lip portion on both sides of the width direction of the outlet slot and forming a variable gap, wherein the flexible spacer is supported by an end of the fixing spacer, is movable so as to adjust the width of the outlet slot, and is configured such that rotation of the adjusting screw moves the second lip portion in the z-axis direction with respect to the first lip portion, such that a position of the y-axis direction of the flexible spacer between the first lip portion and the second lip portion is controlled; and a controller installed on the upper die and arranged to move the second lip portion with respect to the hinge portion to control the variable gap between the first lip portion and the second lip portion.