An ultrasonic jointing method is provided for performing an ultrasonic joint of a conductor part which is exposed by removing a coating of an electric wire with respect to a terminal. The ultrasonic jointing method includes: holding the conductor part of the electric wire and the terminal between an anvil and a horn in which a concave part is formed; and applying an ultrasonic vibration to the conductor part of the electric wire and the terminal that are held between the anvil and the horn. The conductor part is received in the concave part which has a space area of 0.89 to 1.46 times as large as a cross-sectional area of the conductor part of the electric wire.