1. An operation assisting method comprising: comparing input spoken voices with a preliminarily stored keyword associated with an operation target and determining whether or not the keyword is spoken; determining whether or not similarity between or among the input spoken voices falls within a predetermined range, in a case where it is determined that the keyword is not spoken; determining whether or not eyes of a user are directed at the operation target; and in a case of the similarity falling within the predetermined range, determining that the keyword is spoken, in a case of being determined that the eyes of the user are directed at the operation target.