Sixty-three people face charges of accepting bribes, fabricating official documents or leaking military secrets, senior prosecutor Kim Ki-dong told a televised news conference.
The accused include 10 current or former military generals, a former vice minister, businessmen and brokers, according to Kim and the Defense Ministry.
Kim said they were involved in projects to supply the military with body armor, rifles and various equipment loaded at navy ships.
A joint government investigative team has been probing defense procurement projects since November.
South Korea, a vibrant, liberal democracy, is one of the leading economies in Asia, but high-profile corruption scandals still routinely take place.
In March, then-Prime Minster Lee Wan Koo pledged to root out corruption, but he resigned only a month later after being implicated in a widening bribery scandal. Lee and an incumbent provincial governor were later indicted on charges that they took money from a late businessman.