title: Radiation Feedback in Massive Star Formation: Photoevaporation of Accretion Disks authors: Tanaka, K. E. I, and Nakamoto, T abstract: We theoretically examine photoionization feedback on accretion disks around forming massive stars. The massive star formation mechanism has been understood only a little, although massive stars play a lot of important roles in astrophysics. Particularly, it is still an open question that the strong radiation feedback from central massive stars would halt the mass accretion and limit the upper stellar masses which can be formed. To approach this question, we investigate the EUV driven photoevaporation by 2D radiative transfer calculation, and derive an analytic formula of the total photoevaporation rate. We conclude that, once the stellar mass reaches 60Msun, the photoevaporation feedback would halt the mass accretion and may limit the maximum stellar mass.