A conditional processing method and apparatus for efficient memory management are provided. A conditional processing method includes generating a parse tree by loading a plurality of nodes of data structured based on a declarative description language in a memory in series; evaluating, when a parsing switch node having an attribute describing a condition for conditional processing exists among the nodes, child nodes of the parsing switch node according to the attribute; loading only the child nodes fulfilling the attribute in the memory; and outputting the child nodes retained on the memory.