PROBLEM TO BE SOLVED: To provide a foam forming device for bottled carbonated beverage allowing anyone to easily make fine creamy foam.SOLUTION: A foam forming device 100 for bottled beer attached to cover the opening at the upper end of beer bottle 101 comprises: a discharge tube 130 having a beer passage 131 extending from the opening at the upper end of beer bottle 101 to a spout 103 and an ultrasonic speaker 151 which generates ultrasonic waves when a foam forming button 102 is pushed, imparting ultra sonic waves to beer flowing in the beer passage 131 along the way. When the beer bottle 101 to which the foam forming device 100 is attached is inclined for feeding beer inside the beer bottle 101 through the spout 103 to a mug or the like, the foam forming button 102 is pushed to activate the ultrasonic speaker 151. Ultrasonic waves are thus imparted to beer flowing in the beer passage 131 at the contact part of the ultrasonic speaker 151 and the discharge tube 130. As a result, beer having fine creamy foam is discharged from the spout 103.
