Bonding method and method of manufacturing microchannel device

A manufacturing method of manufacturing a microchannel device in which a channel is formed between a first substrate member and a second substrate member which are bonded to each other, the method comprising:

• ultrasonically welding a protruding portion extending on a surface of the first substrate member to a surface of the second substrate member by applying ultrasonic vibration to the first substrate member in a state where a top portion of the protruding portion is pressed against the surface of the second substrate member, the protruding portion corresponding to an edge of the channel,
• wherein 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 the pressed state to be disposed around the protruding portion in the pressed state, and
• 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.