TV footage showed plastic containers brimming with jaw-dropping wads of cash being excavated one after another in the south-western city of Gimje.
Media reports said two brothers who had made the money from an illegal internet gambling operation asked their brother-in-law, surnamed Lee, to hide the cash as police began closing in on them.
One brother is now in jail while the other is still at large.
Lee, 53, bought the garlic field and buried the cash at dusk or dawn, pretending to be working on the land.
But he later dug up about 400 million won ($351,000) and spent it, without telling the brothers.
Because one brother was about to be released from jail, Lee allegedly tried to blame the lost cash on an excavator operator working on the land, but the operator reported the case to police who unearthed the buried bonanza.
Police said they were seeking an arrest warrant for Lee.
Local media said the case underscored the need to crack down on widespread illegal online gambling sites which are based offshore.