Lee Seung-hwan (born October 12, 1993), known professionally as Seo Kang-joon, is a South Korean actor and former singer, who was a member of the group 5urprise. He gained recognition with his role in the television series Cheese in the Trap (2016) and has since starred in Are You Human? (2018), Watcher (2019), When The Weather Is Fine (2020), Grid (2022), Undercover High School (2025), and Boyfriend on Demand (2026).

Filmography

• A Love Other Than Yours — Namgung Ho
• Boyfriend on Demand — Seo Eun-ho
• Undercover High School — Jeong Hae-sung
• Grid — Kim Sae-ha
• 2021A Year-End Medley — Yi-kang
• When the Weather Is Fine — Im Eun-seop
• WATCHER — Kim Young-Koon
• Are You Human? — Nam Shin / Nam Shin III
• Busted! — Kang-Joon Seo
• The Third Charm — On Joon Young
• Idol Fever — Do Yun's older brother
• Cheese in the Trap — Baek In-ho
• Entertainer — Lee Sang-Won
• Entourage — Cha Young-Bin
• Hwajung — Hong Joo-won
• 2015Summer Snow — Sang-gyu
• 2015The Beauty Inside — Woo-jin 92
• To Be Continued — Ah-rin's elder brother
• Cunning Single Lady — Gook Seung-hyun
• 2014My Love, My Bride — Joon-soo
• The Best Future — Choi Go
• What Happens to My Family? — Yoon Eun-Ho
• After School: Lucky or Not
• Good Doctor — One of the punks who wants to beat Shi On
• 2013Haneuljae’s Murder — 尹河
• The Suspicious Housekeeper — Choi Soo Hyuk
• To the Beautiful You — One of the guys putting ghost makeup on Song Jong Min's group
• Law of the Jungle
• KBS Drama Special
• Running Man
• Melon Music Awards — Messenger

Appearances as themselves (3)

• 2014Bomi's Room — Self
• Roommate — Self
• Home Alone — Self