A blow-molding device, which: comprises a blow-molding metal mold (1), a blow nozzle (4) that connects tightly with the mouth tube section (32) of a cylindrical preform that has a bottom (31) when said preform (31) is fitted in the metal mold (1), and an extension rod (8) that is inserted in the axial direction of the blow nozzle (4); and forms a container (41) by longitudinal extension of the preform (31) by means of the extension rod (8) and expanding extension by means of a pressurized liquid (L) supplied via the blow nozzle (4) from a separately provided pressurized liquid supplying section (22). The blow molding device is characterized in that: the blow nozzle (4) comprises a support section (4A) for supporting the orientation of the extension rod (8) and a filling head section (4B) in which a supply path (Fs) for the liquid (L) into the preform (31) is formed in the axial direction and which communicates with the mouth tube section (32) of the preform (31); and the support section (4A) and the filling head section (4B) are configured so as to removably communicate with each other in the vertical direction.
