A communication device comprising: a receiving section adapted to receive, from at least one of one or more external devices, a signal indicating a timing associated with a detection of a state change in the external device, the state change being caused by a predetermined action of a user; an identifying section adapted to identify an external device as a partner device in predetermined communication processing from among the one or more external devices on the basis of a difference between the received timing associated with the detection of the state change in the external device and a stored timing stored in the communication device being equal to or less than a predetermined threshold, thereby determining that the received and stored timing information match each other; a check information retaining section for retaining, as the stored timing, information indicating an assumed timing associated with the detection of a state change in the partner device, the state change being caused by the predetermined action of the user, as check information in advance; and a display control section for displaying, on a display device, information prompting for an action of the user for causing a state change in the partner device when the partner device is to be identified; wherein when the received timing associated with the detection of the state change of the external device indicated by the signal received from one of the one or more external devices and the check information match each other, the identifying section is adapted to identify a transmission source of the signal as the partner device; wherein the predetermined action of the user is an action for making the partner device detect a predetermined state change, wherein the check information retaining section is adapted to retain, as the stored timing, information indicating timing associated with the detection of the state change assumed to be detected in the partner device as the check information in advance, wherein the partner device detects an actual state change caused by the predetermined action of the user, and transmits the signal indicating the timing associated with the detection of the state change, and wherein when the timing associated with the detection of the state change indicated by a signal received from one of the one or more external devices and the timing associated with the detection of the state change indicated by the check information match each other, the identifying section is adapted to identify a transmission source of the signal as the partner device. a receiving section adapted to receive, from at least one of one or more external devices, a signal indicating a timing associated with a detection of a state change in the external device, the state change being caused by a predetermined action of a user; an identifying section adapted to identify an external device as a partner device in predetermined communication processing from among the one or more external devices on the basis of a difference between the received timing associated with the detection of the state change in the external device and a stored timing stored in the communication device being equal to or less than a predetermined threshold, thereby determining that the received and stored timing information match each other; a check information retaining section for retaining, as the stored timing, information indicating an assumed timing associated with the detection of a state change in the partner device, the state change being caused by the predetermined action of the user, as check information in advance; and a display control section for displaying, on a display device, information prompting for an action of the user for causing a state change in the partner device when the partner device is to be identified; wherein when the received timing associated with the detection of the state change of the external device indicated by the signal received from one of the one or more external devices and the check information match each other, the identifying section is adapted to identify a transmission source of the signal as the partner device; wherein the predetermined action of the user is an action for making the partner device detect a predetermined state change, wherein the check information retaining section is adapted to retain, as the stored timing, information indicating timing associated with the detection of the state change assumed to be detected in the partner device as the check information in advance, wherein the partner device detects an actual state change caused by the predetermined action of the user, and transmits the signal indicating the timing associated with the detection of the state change, and wherein when the timing associated with the detection of the state change indicated by a signal received from one of the one or more external devices and the timing associated with the detection of the state change indicated by the check information match each other, the identifying section is adapted to identify a transmission source of the signal as the partner device.