A method of fabricating a halftone phase shift mask is disclosed, by which a process time and a failure ratio can be reduced by sequentially forming a phase shift layer a first photoresist, a metal layer and a second photoresist over a transparent substrate, performing a process to expose a portion of the metal layer, and then performing an etching process to expose a portion of the substrate using the second photoresist as a mask, and then performing an electron-beam exposure process on a portion of the first photoresist such that electrons contact the surface of the transparent substrate, and then simultaneously developing a portion of the first photoresist and removing a portion of the metal layer and a remaining portion of the first photoresist to expose a portion of the phase shift layer.