The present invention provides an active material coating apparatus to form an active material layer having a uniform thickness in a width direction of a substrate when forming the active material layer on a substrate.An active material coating apparatus according to an exemplary embodiment of the present invention includes a lower die having a groove for supplying an active material of a slurry state and forming a first lip portion of an outlet slot connected to the groove and outputting the active material; an upper die disposed on an upper side of the lower die to face the first lip portion, having a second lip portion of the outlet slot, and having a hinge portion at the rear of the second lip portion according to the outlet direction of the active material; a fixing spacer 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 and determining a fixing gap; a flexible spacer 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; and a controller installed to the upper die and pushing/pulling 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.