Acad Sinica, Inst Theoret Phys, Beijing 100080, Peoples R China
; Acad Sinica, Inst High Energy Phys, Beijing 100039, Peoples R China
; Univ Sci & Technol China, Acad Sinica, Grad Sch Beijing, Dept Phys, Beijing 100039, Peoples R China
Pure spinor formalism and non-integrable exponential factors are used for constructing the conformal-invariant wave equation and Lagrangian density for massive fermion. It is proved that canonical Dirac Lagrangian for massive fermion is invariant under induced projective conformal transformations.