This paper estimates the impact of the 52-hour workweek, which was implemented in July 2018, on working hours and employment size of regular workers. The results drawn from the Ministry of Employment and Labor’s “Survey on Labor Conditions by Employment Type” show that the 52-hour workweek reduced the average monthly overtime hours of workers by about 0.648 to 1.030 hours, and that the average monthly total working hours by about 0.723 to 1.557 hours. However, the total employment size of regular workers did not change significantly due to the 52-hour workweek. Analysis that subdivides the sample by workers’ characteristics suggests that the 52-hour workweek increased employment size in some worker groups (56 years old or older and below high school). In the group of mining and manufacturing industries and establishments with more than 300 employees, the 52-hour workweek did not have a significant impact on the employment size of regular workers. On the other hand, in the industry group other than mining and manufacturing, the 52-hour workweek increased the employment size of regular workers.