If the character string is long, and when retrieving symbols containing characters of high frequency of appearance or character chain, high speed retrieval is possible up to infix matching, and a symbol dictionary of small capacity can be compiled. In the symbol dictionary compiling method of the invention, each symbol in symbol data is covered with shorter symbols called “meta-symbols” for covering the symbol in the symbol data, and the information showing how each symbol is covered is obtained by preparing meta-symbol appearance information recorded in each meta-symbol, and therefore high speed retrieval including up to infix matching is possible, and a symbol dictionary of small capacity can be compiled.