Samsung Group Chairman Lee Kun-hee was indicted on charges of tax evasion and breach of trust on Thursday, but was cleared of a more serious bribery charge after a probe into South Korea's biggest business group.
Investors, relieved the four-month investigation had ended, said it may help bring transparency to the murky management structure at Samsung, bringing it closer to global standards.
The investigation was launched in January after a former top legal executive at the group accused some of its top management of hiding money and keeping a slush fund of more than $200 million to bribe politicians, prosecutors and officials.
A special prosecutor indicted nine other senior Samsung executives, but said Lee and the others would not be arrested.
Lee could face from five years to life in prison but analysts say he would likely escape prolonged jail time because judges have often been lenient towards corporate leaders convicted of wrongdoing, saying jailing them could hurt South Korea's economy.
While the prosecutor cleared Samsung of the bribery allegations, he said group officials conspired to hide 4.5 trillion won ($4.55 billion) in Lee's assets and worked secretly to transfer wealth to Lee's children.
In a statement, Samsung apologized "for causing concerns."
"Taking this special prosecution investigation as a new starting point, Samsung is preparing reform plans, based on advice from various sectors of our society," it said, adding it would make an announcement on details next week.
Lee, who was questioned twice this month, said last week he took moral and legal responsibility for the case and would look into reforming management practices at the group.