Magnesium and its alloys are widely used in the industrial field such as the auto-mobile and electronic devices. However, the high reactivity of Mg and its alloys in the aqueous solution limits the application of magnesium. The hydrogen evolution rate on dissolving magnesium is increased when the applied anodic potential is increased, which is called the Negative Difference effect (NDE)1). Some mechanisms related to the anodic dissolution and hydrogen evolution of magnesium have been proposed in previous researches 1-3). Williams et al.2) investigated the local current on the anodically polarized magnesium surface by in-situScanning Vibrating Electrode Technique (SVET). They found that the anodic dissolution of magnesium is shown to be highly localized in nature and accompanied by significant cathodic activity. The reactions for the anodic dissolution of magnesium and hydrogen evolution occurred on the magnesium surface are expressed by the following reactions. Mg → Mg2+ + 2e -(1) 2H2O + 2e - → H2 + 2OH-(2) They2) implied that the hydrogen evolution on the magnesium surface is accelerated by the applied anodic potential. Cain et al.3)supported this theory by investigation using inductively coupled plasma optical emission spectroscopy (ICP-OES) and Rutherford backscattering spectrometry (RBS). However, the anodic dissolution mechanisms of magnesium are not well understood yet. Our group have been investigating magnesium dissolution by 3D impedance spectroscopy. In our previous research, it was found that the inductive loops appeared in impedance spectra of magnesium are originated from Volmer and Heyrovsky reaction by calculating Faraday impedance 4). In the present study, we focus on the localized reaction of magnesium dissolution and hydrogen evolution. The local electrochemical impedance spectroscopy (LEIS)5)combined with 3D impedance spectroscopy was applied to the investigation of anodic dissolution of Mg. Reference: [1] G. Song, A. Atrens, D. Stjohn, J. Nairn, Y. Li, Corrosion Science, 39, 855-875 (1997). [2] G. Williams, N. Birbilis, H.N. McMurray, Electrochemistry Communications, 36, 1-5 (2013). [3] T. Cain, S. B. Madden, N. Birbilis, J. R. Scully, Journal of the Electrochemical Society, 162, C228-C237 (2015). [4] K. Umetsu, Y. Hoshi, I. Shitanda, M. Itagaki 228th ECS meeting abstract, #659 (2016). [5] V. M. Huang, S. Wu, M. E. Orazem, N. Pébère, B. Tribollet, V. Vivier, Electrochimica Acta, 56, 8048-8057 (2011) .