The analysis of scale-up rule for double bubble tubular film process of PA6 was investigated. The scale-up rule previously proposed for a blown film process by the authors was applied to a double bubble tubular film process with a small-scale plant for research (pilot plant) and a large-scale plant for commercial production (production plant). According to the scale-up rule based on the equivalent stretching stress between the pilot and production plants, the equivalence of stretching stability, birefringence pattern and deformation pattern were confirmed. It has been confirmed that the proposed scale-up rule is applicable to predict the physical properties such as film impact strength and the bubble stability for the large-scale tubular film process on the basis of the experimental results obtained from the pilot plant.