The prevalence of autism spectrum disorder (ASD) is increasing worldwide. We investigated the economic burden of ASD in South Korea using a nationally representative data source. The direct medical and non-medical costs, and indirect costs resulting from ASD were estimated. The total prevalence was 5.04 (per 100,000) in 2008, and 10.97 in 2015. The economic cost of ASD was estimated to be $2,700,596 in 2008 and $9,645,503 in 2015. Of the total economic cost in 2015, 72.3% was from direct costs and 27.7% from indirect costs, and 87.5% related to male patients and 12.5% to female patients. The results suggest that the increase in economic costs was greater than the increase in prevalence.