Although the migration behaviors of neurons have been extensively observed and described, the development of glial cells has not been fully understood. We have established in utero electroporation system, and by using this system we visualized the migrating cells derived from the cortical ventricular zone (VZ), and observed the migratory behaviors of them in detail. During these observations, we have noticed a novel population that moves in an unreported irregular manner. These cells frequently change its direction and rate of migration, and they were observed to divide in the IZ. We named this migration mode "erratic migration". To identify the fate of erratic migrating cells, we performed dissociation culture after specific labeling of them by using photoconversion of kikGR during time-lapse observations. We found that the cells that had assumed erratic migration in the slice culture mostly formed colonies of GFAP-positive astrocytes (88%). Moreover, the immunohistochemistry on the slices after time-lapse observations revealed that about 80% of the erratic migrating cells were positive for Olig2, a marker for glial progenitors. These observations indicated that the erratic migrating cells were glia progenitors that mainly produced astrocytes. The fate analysis using Olig2CreER mice revealed that the cortical VZ derived Olig2 expressing cells, which assumed erratic migration in slice culture, mainly differentiated into astrocytes distributed widely in the cortical gray matter. On the other hand, the VZ cells labeled by electroporation after birth (on the day of birth or postnatal day 1) produced few or no erratic migrating cells, and mainly differentiated into astrocytes in the white matter or deep pert of the gray matter.