An injection needle unit includes a plurality of injection needles, a plate-shaped member that has a first surface for holding a proximal portion of the plurality of injection needles, and a lid member that is disposed so as to face a second surface which is a back surface of the first surface of the plate-shaped member. The plate-shaped member has a first groove which connects a supply tube for supplying the liquid to the second surface and a second groove which distributes the liquid to the plurality of injection needles. The lid member has a third groove in a region where the first groove and the second groove face each other.
