A halftone type phase shift mask blank including, on a transparent substrate, at least a phase shifter film having a predetermined transmittance for an exposed light and a predetermined phase difference for the transparent substrate, wherein the phase shifter film is formed by a multilayer film in which films including at least two layers having an upper layer formed on the most surface side and a lower layer formed thereunder are provided, and a thickness of the upper layer is adjusted in such a manner that a refractive index of the film to be the upper layer is smaller than that of the film to be the lower layer and a surface reflectance for the inspecting light of the phase shifter film is maximized and approximates to a maximum.