A cylindrical preform (1) for producing liquid containers for medical use, said cylindrical preform (1) being formed by injection molding a thermoplastic resin and comprising a closed upper end part (3), a lower end part (4) forming a discharge part (44), and a cylindrical main body part (2) connecting the closed upper end part (3) to the lower end part (4), wherein: the closed upper end part (3) is provided with a wall thickness change part (31), where the wall thickness is gradually decreased upward, for forming an inwardly deformable part of a liquid container (10) for medical use. In the wall thickness change part (31), the wall thickness (a) at the upper end of the wall thickness change part (31) is 1.3-1.6 mm and the wall thickness (b) at the lower end of the wall thickness change part is 2.5-4 times as large as the wall thickness (a).
