1. A text generation method for generating text of a sentence or paragraph in a predetermined language using a text generation device, comprising: inputting one or more words as keywords into the text generation device; generating phrase candidates in the text generation device from the keywords by searching for and extracting from a corpus sentences or phrases containing each keyword; generating text candidates of a sentence or paragraph in the text generation device assuming a syntactic dependency relation among the phrase candidates; evaluating the text candidates generated in the text generation device; converting the text candidates generated in the text generation device to surface sentences; and outputting at least one of the surface sentences.