The notion of dually flatness is of central importance in information geometry. Nevertheless, little is known about dually flat structures on quantum statistical manifolds except that the Bogoliubov metric admits a global dually flat structure on a quantum state space {{mathcal {S}}}({{mathbb {C}}}^d) for any dge 2. In this paper, we show that every monotone metric on a two-level quantum state space {{mathcal {S}}}({{mathbb {C}}}^2) admits a local dually flat structure.