In recent polymorphism studies of gallium phthalocyanines, a new crystal form of hydroxygallium phthalocyanine (Type V HOGaPc) was obtained. It shows an extremely high photosensitivity (E_1/2 = 1.3 mJ/m⁺² at 780 nm) and excellent thermal stability. Furthermore, its photosensitivity is not affected by changing humidity. Hence, it is an useful charge generation material for an IR photoreceptor. From the TGA and Rietveld analysis of the Type V crystal, it is indicated that the highly photosensitive characteristic of this pigment does not depend on sensitization by water. The high sensitivity is attributed to the specific crystal structure and to the presence of the hydroxyl group, both of which are favorable for charge generation.