A phase shift mask manufacturing method comprises the steps of processing a light-shielding layer over a transparent substrate into a predetermined light-shielding pattern, forming a resist film on the predetermined light-shielding pattern, performing writing on the resist film based on writing data and developing the resist film, thereby forming a resist pattern, and etching an underlying layer using the predetermined light-shielding pattern and the resist pattern as a mask, thereby forming recesses, that serve as phase shift portions, in the underlying layer. The writing data includes a portion where pattern data corresponding to at least the two recesses adjacent to each other through a light-shielding portion in the predetermined light-shielding pattern are combined into one pattern data.