In February 2021, the bill, removed provisions that prohibited the payment of wages to full time union officer, passed in the National Assembly as an acceptance of recommendations raised in the agreement of ILO thereby changes in activity contents of labor unions are expected. In the present study, the trend and changes in distributed times for the past five key activities of labor unions within the limit of time-off system were observed. The key activities dominant among entire hours granted by the time-off system were occupied by the collective bargaining on determination of level of wages, which appeared increasing by 1.38% in 2019 comparing to that of 2013 except for other activities of labor unions. Contrastingly, the increase in distributed times for the activities of the Industrial Safety and Health Committee is still negligible despite its increase by 23.47% comparing to that in 2013. The total amount of hours granted by time-off system is expected to be increasing to a certain extent as an effect of legislation. In this case, the increase in activities to prevent industrial disasters and improvement in times granted by the time-off system biased to collective bargaining of wages is needed. Thus the government is suggested to support both employers and employees to get reasonable balance of times granted by the time-off system through monitoring and pertinent consult in gadded to regular factual surveys of respective industries. And it is also needed to socially propagate the recognition of activities, to prevent industrial disasters by labor unions through exploiting the time-off system, as soc