Meltblown nonwovens market has been continuing to grow because of the unique characteristics of allowing the production of microfiber webs directly from a thermoplastic polymer in a single step. Whereas a vast majority of meltblown processes have utilized the traditional Exxon die, the Biax-die has also been used in some processes. The aim of this study was to understand the effect of critical process conditions of the Biax process, which has the advantage of lower high pressure hot air consumption compared to the traditional process, on the structure of meltblown webs. As the performance properties of meltblown nonwovens are mainly determined by the fiber diameter and diameter distribution, this study focused on these two characteristics considering various process conditions such as melt temperature, melt throughput, air temperature and air pressure. In conclusion, it was observed that there were three distribution types, the normal distribution, log-normal distribution, and skewed log-normal distribution, for meltblown webs produced by the Biax process. Air pressure and melt throughput were the most effective process conditions on the fiber diameter of meltblown polypropylene webs. It was also observed that fine fiber webs close to one-micron average fiber diameter and relatively narrower fiber diameter distribution can be produced under appropriate processing conditions using the Biax process.