A wearable device comprising: a main body configured to be worn by a user; a sensing unit configured to sense a biological signal of the user; a storage unit configured to store log information (310, 320, 330, 340, 350, 360, 370); a user notification unit configured to output feedback; a controller configured to: collect log information including information relating to the biological signal of the user and information relating to a state of the user; store an index pattern, in the storage unit, that indicates a correspondence between the information relating to the biological signal of the user with the information relating to the state of the user that are included in the collected log information, determine a reference driving index that indicates values of the stored index pattern that are suitable for the user to drive a vehicle; and sense that the user gets on the vehicle through a predetermined input signal at the wearable device, based on detecting a vehicle entry event for the user, calculate a current driving index corresponding to the biological signal that is sensed before and after the user gets in the vehicle, with the reference driving index stored in the storage unit serving as a reference, and wherein the controller outputs feedback by the user notification unit that notifies the state of the user, which corresponds to the calculated current driving index. a main body configured to be worn by a user; a sensing unit configured to sense a biological signal of the user; a storage unit configured to store log information (310, 320, 330, 340, 350, 360, 370); a user notification unit configured to output feedback; a controller configured to: collect log information including information relating to the biological signal of the user and information relating to a state of the user; store an index pattern, in the storage unit, that indicates a correspondence between the information relating to the biological signal of the user with the information relating to the state of the user that are included in the collected log information, determine a reference driving index that indicates values of the stored index pattern that are suitable for the user to drive a vehicle; and sense that the user gets on the vehicle through a predetermined input signal at the wearable device, based on detecting a vehicle entry event for the user, calculate a current driving index corresponding to the biological signal that is sensed before and after the user gets in the vehicle, with the reference driving index stored in the storage unit serving as a reference, and wherein the controller outputs feedback by the user notification unit that notifies the state of the user, which corresponds to the calculated current driving index. collect log information including information relating to the biological signal of the user and information relating to a state of the user; store an index pattern, in the storage unit, that indicates a correspondence between the information relating to the biological signal of the user with the information relating to the state of the user that are included in the collected log information, determine a reference driving index that indicates values of the stored index pattern that are suitable for the user to drive a vehicle; and sense that the user gets on the vehicle through a predetermined input signal at the wearable device, based on detecting a vehicle entry event for the user, calculate a current driving index corresponding to the biological signal that is sensed before and after the user gets in the vehicle, with the reference driving index stored in the storage unit serving as a reference, and wherein the controller outputs feedback by the user notification unit that notifies the state of the user, which corresponds to the calculated current driving index.