The present invention provides a method for producing active hepatocyte growth factor activator (HGFA) and active hepatocyte growth factor (HGF) without using animal serum. The present invention relates to a method for producing active HGFA without using animal serum. The method is characterized in that it comprises a step of obtaining a culture supernatant comprising pro-HGFA by culturing mammalian cells expressing inactive hepatocyte growth factor activator (pro-HGFA) in a medium without serum, and a step of adjusting the culture supernatant comprising pro-HGFA obtained in the above step to weakly acidic to convert pro-HGFA into active HGFA. The present invention also relates to a method for producing active HGF with HGFA produced by said method.