Lipases have substrate specificities, such as fatty acid specificity, alcohol specificity, positional specificity and so on, and catalyze hydrolysis, esterification, and transesterification. Combination of the substrate specificity and catalyzed-reaction creates a valuable process for oil and fat processing, which can not be achieved by chemical processes. In this paper, production of functional oils and fats, purification of useful materials from natural oil resources, and conversion of unutilized oil resources to biodiesel fuel by lipase-catalyzed reactions are described.