1. An authentication apparatus comprising: a functional part carrying out a predetermined function to be used by a user; electromyogram acquiring means for measuring a change of an electromyogram caused by a motion of a muscle of the user; transmitting means for transmitting a result of the measurement by the electromyogram acquiring means, to a predetermined destination apparatus; receiving means for receiving a result of authentication of the user returned based on the result of the measurement transmitted; and state transition means for implementing a transition into a state in which the user can use the predetermined function of the functional part, according to the result of the authentication received.