Provided are a command input device, a mobile information device, and a command input method which can easily be operated by a user even when the input unit in the device is small. A first and a second detection modules arranged on a device which is brought into contact with a user body detect vibration caused by a tapping operation on the user body and transmitted via the user body. The position of the tapping operation on the user body is identified according to analysis data obtained by analyzing the vibration relations detected by the first and the second detection modules such as a known correspondence between a time difference between the detection timings and the position of the tapping operation on the user body. Since the user body can be used as a space for inputting a command, it is possible to secure a sufficient input space.