A rapidly outgrowing tumor mass is liable to suffer from a shortage of oxygen and nutrients due to the diffusion limit. These features evidently prevail in glioblastoma, resulting in extensive hypoxic regions throughout the tumor mass. While there may be a strong link between hypoxic regions and glioblastoma malignancy, the effects of hypoxia stress on each tumorigenic step and their interrelation during the progression remain unexplored due to the limited information from current assay platforms. Here, we suggest a tumor microenvironment array platform (TMAP) to describe a time series assessment of glioblastoma tumorsphere (TS) within a microscale niche. TMAP enables to observe the overall tumorigenic process of glioblastoma TSs over the cultivation time, simultaneously quantifying the features with the biophysical parameters. Through the time series assessment, we observed the induction of hypoxic stress within the mature TSs, which rendered intratumoral phenotypic changes to become more malignant and modulated their microenvironmental niches to enhance angiogenic proliferation, immune recruitment, and even drug response. Based on the finding that the tumorigenic parameters were highly correlated only in mature TSs, we conclude that the effects of hypoxic stress systematically affect the process that drives a glioblastoma to higher malignancy.