An ultrasonic welding device includes a rotary support mechanical assembly rotatable about a rotation axis and operable to support a sheet over a circumference centered on the rotation axis, the sheet being continuously supplied； a horn and an anvil attached to the rotary support mechanical assembly to thereby revolve about the rotation axis and sandwich the sheet supported over the rotary support mechanical assembly to weld the sheet； a cam drum and a cam follower for driving the anvil in such a manner that the anvil moves relative to the horn； a holding member body； and a power transmission mechanism for distributing a power generated by the cam and the cam follower in such a manner the power is transmitted to the anvil and holding member body in opposite directions.
