Provided is a method of producing polypropylene. More specifically, provided is a method of efficiently producing high-strength isotactic polypropylene having high crystallinity even with a shorter polymerization time. More specifically, provided is a method of producing polypropylene, including polymerizing propylene in the presence of a catalyst composition including a Ziegler-Natta catalyst, an external electron donor, dialkylaluminum hydride, and trialkylaluminum. The polypropylene has a xylene cold soluble content of 3 wt % or less.