A preform formed from polypropylene or high density polyethylene and with which a container of a desired shape can be precisely molded by liquid blow molding. When formed of polypropylene as a closed-bottom cylinder shape having an open end section and a body section, the preform is molded into the container by stretching the body section in the axial direction by a stretch ratio of 2.25-4.34, inclusive, and in the radial direction by a stretch ratio of 1.95-5.00, inclusive. When formed of high density polyethylene as a closed-bottom cylinder shape having an open end section and a body section, the preform is molded into the container by stretching the body section in the axial direction by a stretch ratio of 1.69-2.50, inclusive, and in the radial direction by a stretch ratio of 2.26-5.07, inclusive.