To understand the brain, it is essential to understand neuronal electrophysiological properties. The Allen Brain Atlas Data Portal contains extensive data recorded from neurons in the mouse visual cortex. Here, the electrophysiological properties of excitatory and inhibitory neurons were compared on the basis of the data provided. As is well known, most inhibitory neurons are characterized as fast-spiking neurons, and most excitatory neurons are characterized as regular-spiking neurons. Inhibitory interneurons show a broader range of electrophysiological properties. However, the characteristics of the two cell types overlap, as outliers are observed in both groups. Therefore, it is necessary to not only study the electrophysiological characteristics of individual neurons but also to consider morphological and molecular characteristics to understand neuronal function.