13. A specific call detecting method comprising: in a call between a first speaker and a second speaker, detecting at least a first utterance period, from among the first utterance period in which the first speaker speaks from first voice uttered by the first speaker and obtained by a voice input unit, and a second utterance period in which the second speaker speaks from a second voice uttered by the second speaker; calculating utterance ratio of the first speaker in the call on the basis of at least the first utterance period among the first and second utterance periods; determining whether at least one of the first and second voices is to be a target of voice recognition or not on the basis of the utterance ratio; detecting a keyword related to a specific call from the voice determined as a target of voice recognition among the first and second voices; and calculating an evaluation value so that the larger the number of keywords detected is, the higher the evaluation value indicative of probability of the specific call is, and when the evaluation value is equal to or higher than a predetermined threshold, determining that the call is the specific call.
13. A specific call detecting method comprising: in a call between a first speaker and a second speaker, detecting at least a first utterance period, from among the first utterance period in which the first speaker speaks from first voice uttered by the first speaker and obtained by a voice input unit, and a second utterance period in which the second speaker speaks from a second voice uttered by the second speaker; calculating utterance ratio of the first speaker in the call on the basis of at least the first utterance period among the first and second utterance periods; determining whether at least one of the first and second voices is to be a target of voice recognition or not on the basis of the utterance ratio; detecting a keyword related to a specific call from the voice determined as a target of voice recognition among the first and second voices; and calculating an evaluation value so that the larger the number of keywords detected is, the higher the evaluation value indicative of probability of the specific call is, and when the evaluation value is equal to or higher than a predetermined threshold, determining that the call is the specific call. 14. The specific call detecting method according to claim 13 , wherein the determining whether at least one of the first and second voices is to be a target of voice recognition or not, determines that the first voice is a target of voice recognition until a period in which the utterance ratio is higher than a predetermined threshold, reaches a first period, and determines that the first voice is not a target of voice recognition after the period in which the utterance ratio is higher than the threshold, reaches the first period.