Onboard information device mounted on vehicle to provide information for supporting passenger includes voice acquisition unit that continually detects and acquires voice the passenger utters while the onboard information device is operating; voice recognition unit that recognizes speech contents of the voice the voice acquisition unit acquires; vehicle state detector that detects vehicle state including environmental state in the vehicle, surrounding state of the vehicle or operating state of the vehicle; output controller that creates display data or voice data from the speech contents recognized by the voice recognition unit according to the vehicle state the vehicle state detector detects, and that controls output of the display data or voice data; and output unit that outputs the display data or voice data the output controller creates. It can perform effective conversation support in real time according to recognition result obtained by continually recognizing speech contents of the passenger.