Disclosed is a shadow mask having a fine slit that can improve precision and resolution of a pattern by reducing side etching during an etching process of a mask substrate, and a manufacturing method thereof. The shadow mask includes a mask substrate, a slit region formed by penetrating through the mask substrate, the slit region having a plurality of undercut portions at respective sides thereof, each undercut portion having a unit thickness, and a shadow region provided in the mask substrate, the shadow region corresponding to a region other than the slit region.