The move comes ahead of Francis' planned visit later this year to South Korea, where he will attend the Asian Youth Days celebrations in Daejeon. The formal beatification ceremony is expected to take place on Aug 15.
The pontiff recognised the martyrdom of Paul Yun Ji-chung and of his 123 companions, the Vatican said in a statement. They were among an estimated 10,000 Koreans killed for renouncing Confucianism between 1791 and 1888.
Beatification is the last formal step in the Roman Catholic church before canonisation and sainthood.
In another nod to the Korean Catholic Church, Francis last month included Seoul Archbishop Andrew Yeom Soo-jung among the list of 16 new cardinals to be formally appointed in a Feb 22 ceremony at the Vatican.
Roughly 8% of South Korea's 49 million people are Roman Catholics.
A first group of 103 Korean martyrs from the 19th century were beatified by John Paul II in 1984. He was the last pope to visit South Korea, in 1989.