영남대학교
However, Son decided to enter the Unicorns after graduation from college and continued to play baseball as a pitcher at Yeungnam University in Daegu. At Yeungnam University, he developed into one of the top collegiate pitchers along with Oh Seung-Hwan and Jang Won-Sam. As a sophomore in , Son was called up to the Under-22 South Korea national team for the inaugural World University Baseball Championship held in Messina, Italy. In , Son was selected for the South Korean national team as an amateur player and participated in the Baseball World Cup held in Havana, Cuba. At the World Cup, he led team in innings pitched with 18.1 and earned a save against Italy in the round-robin stage.