Post-editing of machine translation has gained public attention thanks to its arguably high productivity and reasonable quality of the product. While the use of machine translation and post-editing increased, there have not been adequate assessment and deliberations on the productivity and quality of English to Korean post-editing. This study attempts to compare the human translation and post-editing products and assess their productivity. The analysis shows that the productivity of post-editing is higher than that of human translation in general. However, participants showed significant differences in the level of productivity gain, and some participants achieved high productivity at the cost of quality. Furthermore, participants showed different error correction behaviors when the text becomes more difficult. In this regard, it is reasonable to argue that English to Korean post-editing can help enhance translation productivity, but it is advisable to consider the factors that may negatively affect productivity and quality.