An input device includes a plurality of input keys arranged in a matrix of three or more rows and three or more columns; electrodes facing parts of or all surfaces of the input keys that surround intersection of rows and columns formed by the arrangement of the input keys; and an input key detecting unit that identifies operated input keys among the plurality of input keys by combinations of the electrodes having a change in electrostatic capacitance. With this structure, the number of electrodes can be less than that of the input keys.