(Proposal ID) S11B-048 (PI) Yabe, Kiyoto (Proposal Title) Mass-metallicity relation of star-forming galaxies at z ~ 1.4 (Abstract) Gas metallicity is a key parameter to know stage of galaxy evolution because it reflects a result of past star-formation activity in a galaxy, and deriving mass-metallicity relation and tracing its cosmological evolution are very fundamental to understand the galaxy evolution. Although the local stellar mass-metallicity relation is established at z ~ 0.1 based on SDSS galaxies, the relation at higher redshift is still debated mainly due to the small size of sample. In order to establish the mass-metallicity relation for star-forming galaxies at z ~> 1 and to delineate cosmological evolution of the mass- metallicity relation, a much larger sample is absolutely necessary. Recently, we observed star-forming galaxies at z ~ 1.4. Preliminary results show that metallicity of the galaxies at z ~ 1.4 is located between the mass-metallicity relations at z ~ 0.1 and z ~ 2.2 with a slight down-sizing trend. We also found that galaxies with higher star-formation rates tend to show the lower metallicity at a fixed stellar mass. The sample size, however, is not large enough to investigate further details. Here we propose further observations with FMOS to enlarge our sample, to consolidate the mass-metallicity relation at the redshift, and to examine whether SFR (and possible other parameters) affects the metallicity.