1. A speech recognition device comprising: a processor; and a memory which stores a plurality of instructions, which when executed by the processor, cause the processor to execute, conducting a search, by speech recognition, on audio data stored in a first memory to extract wordspoken portions where plural words transferred are each spoken and, of the word-spoken portions extracted, rejects the word-spoken portion for the word designated as a rejecting object; obtaining a derived word of a designated search target word, the derived word being generated in accordance with a derived word generation rule stored in a second memory or read out from the second memory where the derived word is stored in association with the search target word, and sets the derived word to an outputting object or the rejecting object according to setting designation information or a user's instruction, the setting designation information being stored in the second memory and indicating whether the derived word is the outputting object or the rejecting object; transferring the derived word and the search target word to the conducting, the derived word being obtained and set to the outputting object or the rejecting object by the obtaining; and outputting the word-spoken portion extracted and not rejected in the search of the conducting, wherein the derived word generation rule is generated based on a difference between the search target word and a derived word that is stored in the second memory.