A bonding method for a conductor of an electric wire including a conductor formed of a plurality of strands and a sheath covering the conductor such that the conductor is exposed to a predetermined length. The bonding method includes bonding the strands to each other, the strands being spaced apart from the sheath by a predetermined length. An outer diameter of a middle portion of the conductor between a bonded portion and a portion covered with the sheath gradually decreases toward the bonded portion. A maximum value of an intersection angle between an upper surface of the bonded portion or a longitudinal direction of the electric wire and the strands of the middle portion is smaller than a predetermined angle. The predetermined angle is an angle at which breakage of the strands is prevented when the bonding is performed.