To provide parison expanding equipment of a blow molding machine which can change fitting positions of opening-closing cylinders in no stages, with ease and in a short time.

One end of a cylinder fitting metal implement 3 is fitted pivotally to the rear end of each of a pair of opening-closing cylinders 32 which move a pair of parison expanding members 31 back and forth, while the other end of the cylinder fitting metal implement 3 is fitted slidably to a guide rod 1 provided on an elevating frame 33. Thereby fitting positions of the opening- closing cylinders 32 are made changeable in no stages in accordance with a dimension between opening parts of a molded article (dimension between expanding pins).