1. A method of measuring a biosignal, the method comprising: determining whether an attached wearable mobile device is closely attached to a user or loosely attached to the user; and providing a biosignal-based service in response to the wearable mobile device being determined to be closely attached to the user and providing a non-biosignal-based service to the user in response to the wearable mobile device being determined to be loosely attached to the user, wherein the determining comprises: measuring a range or a position at which the wearable mobile device contacts the user; determining that the wearable mobile device is closely attached to the user in response to the measured range satisfying a standard value or in response to the measured position corresponding to a skin area of the user; and determining that the wearable mobile device is loosely attached to the user when the wearable mobile device is located at a wrist area of the user; and wherein the standard value and the skin area of the user correspond to the wearable mobile device being positioned at a skin area of the user that has greater circumference than a wrist area of the user.