Farm power transition from man power and animal power to mechanical power has been in progress in the tillage operation on paddy fields in Sri Lanka. In contrast to small paddy farmers in Japan, Sri Lankan farmers whose family income is not adequately supported by non-farm jobs are financially incapable of keeping their own farm machines. Nevertheless, farm mechanization is in progress. Thousands of small farmers living below the poverty line use farm machines hired from the farm power owners. Farm power owners, by virtue of their monopoly over the farm power hire market successfully pass on the increased costs on machines to the hirers by raising the hire rates. At the first sight, it seems to be difficult to find rational grounds for Sri Lankan farmers’ tendency towards mechanization. However, it has been observed in a number of micro-level socio-economic surveys that the scarcity of man power, animal power, time and water during the rather short ploughing period generates compelling grounds for farmers to substitute mechanical power for animal power. This study is intended to observe this contention at the national level. Multiple regression analysis based on country-wide cross-sectional data suggests that 51 % of the spatial variation in the degree of mechanization is associated with the factors pertaining to the scarcity of man power, animal power, time and water during the ploughing period. These factors may collectively generate grounds which encourage or enforce small paddy farmers to adopt mechanical power despite they are not in a real position to afford.