To provide a liquid introduction unit that can stably open and close a valve body even when a film is warped, and to provide a liquid injection head unit, and a method for manufacturing the liquid introduction unit.

The liquid introduction unit 44 includes: a liquid flow path 38; a pressure chamber 40 sealed at one surface thereof with a film 39; a valve body 42 for opening and closing a communication part 41 between the pressure chamber 40 and an upstream side; and a pressure receiving member 43 facing the valve body 42. The pressure receiving member 43 has a shaft part 43a serving as a rotation axis and a pressure receiving part 43b for pressing the valve body 42. The liquid introduction unit 13 opens and closes the communication part 41 according to pressure changes in the pressure chamber 40. The liquid introduction unit 44 has a bearing part 65 for holding the shaft part 43a, which is provided with a welded part 68 where a part of the film 39 is welded to a tip end close to the film. At least a part of the welded part 68 is protruded between the film 39 and the shaft part 43a to restrict movement of the shaft part 43a in a film direction by the protruded part.