Abstract This paper systematically investigates the comoving megaparsec-scale intergalactic medium (IGM) environment around galaxies traced by the Lyα forest. Using our cosmological hydrodynamic simulations, we investigate the IGM–galaxy connection at z = 2 by two methods: (i) cross-correlation analysis between galaxies and the fluctuation of Lyα forest transmission (δ _F) and (ii) comparison of the overdensity of neutral hydrogen (H i) and galaxies. Our simulations reproduce observed cross-correlation functions (CCFs) between Lyα forest and Lyman-break galaxies. We further investigate the variation of the CCF using subsamples divided by dark matter halo mass (M _DH), galaxy stellar mass (M _⋆), and star formation rate (SFR) and find that the CCF signal becomes stronger with increasing M _DH, M _⋆, and SFR. The CCFs between galaxies and gas density fluctuation are also found to have similar trends. Therefore, the variation of δ _F–CCF depending on M _DH, M _⋆, and SFR is due to varying gas densities around galaxies. We find that the correlation between galaxies and the IGM H i distribution strongly depends on M _DH as expected from linear theory. Our results support the ΛCDM paradigm, confirming a spatial correlation between galaxies and IGM H i, with more massive galaxies being clustered in higher-density regions.