Method of inspecting leakage of inner container in double blow molded bottle body

This invention provides double blow molded bottles of synthetic resins, which are given consistent quality by making it possible to detect the existence of a leak in the inner vessel in which to store the liquid contents. The bottles of consistent quality can be provided by a method of leak test, which comprises forming an air channel (10) between an outer vessel (2) and said inner vessel (3) by deflating and peeling said inner vessel (3) from said outer vessel (2) and by securing air flow through an opening (5) of said air channel (10), and judging the existence or non-existence of a leak through the wall of said inner vessel (3) by supplying air to said inner vessel (3) at a given micropressure and by observing, after a certain period of elapsed time, whether or not the pressure inside said inner vessel (3) reaches the predetermined level which has been set from a test conducted under the same conditions using the bottles (1) with no leak through the wall of said inner vessel (3).