A bonding method includes ultrasonically welding a protruding portion extending on a surface of a first substrate member to a surface of a second substrate member by applying ultrasonic vibration to the first substrate member. A protruding stopper portion for stopping welding is provided on the surface of the first substrate member formed with the protruding portion, or on the surface of the second substrate member to come in contact with the protruding portion in a pressed state, to be disposed around the protruding portion in the pressed state. The ultrasonically welding includes a first process for applying ultrasonic vibration at amplitude as a first value to the first substrate member, and a second process for applying ultrasonic vibration to the first substrate member at amplitude as a second value lower than the first value after the first process.