1. A navigation apparatus including a voice input unit that receives an instruction by voice input, and a voice recognition unit that carries out voice recognition of the instruction received by the voice input unit, the navigation apparatus comprising: a recognition vocabulary comprehension level deciding unit that decides a user comprehension level of a recognition vocabulary, which is an instruction recognizable by the voice recognition unit, from at least one of correction operation frequency and time-out frequency in an operation which is carried out during the voice recognition by the voice recognition unit and corresponds to the instruction; an operational transition determining unit that determines an operational transition which is defined by guidance, an operational procedure, an operation screen and the recognition vocabulary in accordance with a decision result of the recognition vocabulary comprehension level deciding unit; and an operational transition providing unit that provides the operational transition determined by the operational transition determining unit.