The skewed distribution has been observed in natural disaster, economy, and so on. The current high proportion of the COVID-19 confirmed cases in the Seoul Metropolitan Area seems to be its another case. The standard economics fails to explain them since it mainly assumes the normal distribution. Thus, this paper attempts to examine the pattern of COVID-19 cases occurrence in the framework of complex network and explore the uncertain effect of the social distancing policy. The results showed the distribution of COVID-19 cases followed a power law distribution with a fatter tail than the population distribution. Also we confirmed that the social distancing policy has a limited effect in the high population density area like Seoul Metropolitan Area because of the self-organization mechanism of large-scale network. This study implies that the complex network approach is necessary to better understand the contemporary socioeconomic system.