Mechanization is a solution for agricultural workforce scarcity, especially in rice farming. This paper aims to study performances and impacts of harvesting and threshing machines on labor institution of rice farming. This research employed survey data of National Farmer's Panel study conducted by ICASEPS in 2010 and 2015 in wetland agro-ecosystems in Sidrap, Karawang, and Subang Regencies. Data were analyzed descriptively. Mechanization technologies were more efficient in terms of number and time of labor use compared to that of traditional. Negative impact of the machines was share croppers elimination because the land owner tended to cultivate their own farm land. Some labor lose their job opportunity, some got less income from local income share system. Farmers were unprepared to manage agricultural machinery. It is necessary to provide alternative employment for the affected workers. Agricultural mechanization needs to deal with existing traditional labor institutions to having mutual benefit.