The present invention refers to a method of preparing a separator, a separator prepared therefrom and an electrochemical device having the separator. The method of preparing a separator according to the present invention comprises providing a planar and porous substrate having multiple pores; and coating a first slurry on at least one surface of the porous substrate through a slot section to form a porous coating layer, while continuously coating a second slurry on the porous coating layer through a slide section adjacent to the slot section to form a layer for adhesion with an electrode, the first slurry comprising inorganic particles, a first binder polymer and a first solvent, and the second slurry comprising a second binder polymer and a second solvent. In accordance with the present invention, in the preparation of a separator, a second slurry comprising a binder polymer is smoothly discharged through a slide section without an external force to coat a layer for adhesion with an electrode on the top of a porous coating layer which is formed on a porous substrate by discharging a first slurry through a slot section, thereby preventing the inter-mixing of the porous coating layer and the layer for adhesion with an electrode, and eventually improving the adhesiveness of the separator to an electrode and preventing the performance of an electrochemical device from being deteriorated.