A speech processing apparatus includes a sound input unit that receives an input of a sound including a voice of one of an operator and a person other than the operator; a designation-duration accepting unit that accepts a designation-duration designated by the operator as a time interval that is a target of a speech processing within the input sound; a voice-duration detecting unit that detects a voice-duration that is a time interval in which the voice is present from the input sound; a speaker determining unit that determines whether a speaker of the voice is the operator or the person based on the input sound; and a deciding unit that detects an overlapping period between the designation-duration and the voice-duration, and decides that the voice-duration including the overlapping period is a processing duration, when the overlapping period is detected and the speaker is determined to be the person.