Electrical activities of neuronal network with high-spatio-temporal resolution is useful for understanding brain functions and elucidating neurological disorders, and for drug screening and safety assessment of drugs. Complementary metal-oxide semiconductor micro-electrode array (CMOS-MEA) is excellent in detecting detailed electrical activity patterns of neural networks due to the large number of electrodes. In this study, we investigated the electrical activity characteristics of brain slices, brain organoids, and cultured neural networks using CMOS-MEA with 236,880 electrodes, which have the highest specifications in the world. In the measurement of brain slices, we succeeded in measuring the interregional propagation of the hippocampus and cerebral cortex area in detail, and detected changes of propagation patterns due to drug administration. In sensory neuron measurement, calculation of axon conduction velocity in single neuron and drug responses based on firing pattern of each neuron were detected. In human iPS cell-derived central nervous system networks and human cerebral organoids, network activity was detected on a cell-by-cell basis, and changes in propagation patterns due to drug administration were detected. It was found that CMOS-MEA with 236,880 electrodes and a large measurement area can measure the electrical activity characteristics of ex vivo and in vitro neural networks and single neuron in detail. It was suggested that big data with high temporal resolution is effective for elucidation of neural circuit function and drug evaluation based on new neural activity information.