Atacama Large Millimeter/submillimeter Array (ALMA) has enabled us to detect [Oiii] 88 μm line even at z > 9. To study the properties of high-redshift [Oiii] emitters, we calculate [Oiii] luminosities of galaxies in a cosmological simulation by applying a physical model of Hii region and using the photoionization code cloudy. We find that the [Oiii] 88 μm luminosity, LOIII,88, scales with SFR with slightly larger LOIII,88 than a local relation. Some [Oiii] emitters have extended disk-like structure. We propose to use the ratio between [Oiii] 88 μm line and [Oiii] 5007 Å line, which can be detected with James Webb Space Telescope (JWST), to estimate the gas density and the metallicity in HII region of high-redshift [Oiii] emitters.