1. A machine translation method for translating from a first language to a second language through the use of a base dictionary and at least one domain dictionary, in which said domain dictionary includes at least one of a first compound word dictionary and a first single word dictionary that includes triggers for changing priorities of dictionaries and at least one of a second compound word dictionary and a second single word dictionary that does not include said triggers for changing the priorities of dictionaries, said machine translation method comprising: inputting a source text of said first language; analyzing said inputted source text to determine at least one of a compound word and a single word that is used in said source text; judging whether at least one of said determined compound and single words is included in at least one of said first compound word dictionary and said first single word dictionary; setting a priority of a dictionary including at least one of said first compound word and single word dictionaries higher than that of said base dictionary if said judgment is true; and creating a translated sentence of said second language through the use of said dictionary having the priority set higher.