(Proposal ID) S17A-049 (PI) Onodera, Masato (Proposal Title) Spectroscopic identification of extreme emission line galaxies at z>3 (Abstract) Star-forming galaxies with extreme emission line strengths appear to be ubiquitous in the early universe and play a dominant role in producing ionizing photons causing the cosmic reionization. Since they are too faint to carry out a detailed spectroscopic follow-up, lower redshift analogs, so-called extreme emission line galaxies (EELGs) have been studied extensively at z < 3. Here, taking an advantage of the improved sensitivity of the upgraded MOIRCS, we propose to carry out a systematic spectroscopic follow-up of EELG candidates at even higher redshift of z > 3 selected as K-broad band excess objects as very strong H beta and [O{III}] lambda4959,5007 elevate their K-band fluxes. Our primary aim is to identify EELGs at z>3 based on the emission line equivalent widths. For the identified EELGs, we will further investigate the metallicity, ionization condition, photometric redshift calibration, and accurate stellar. The identification of still nearly unexplored population of EELGs at z > 3 enables us to constrain the early phase of galaxy formation and evolution, and to find a clue to understand the process of cosmic reionization.