The present technology relates to an information processor and an information processing method that enable presentation of a response to a user with an appropriate amount of information in a voice interaction system. Provision of an information processor including a processing unit that adjusts an amount of information in a response with respect to desired information of a user, in accordance with a certainty factor of the user himself/herself that is estimated for the desired information makes it is possible to present the response to the user with the appropriate amount of information in the voice interaction system. The present technology is applicable to a voice interaction system, for example.