I recommend Masan Yangdeok <Seoul Children's Hospital>.

My nephew had a high fever and severe lower abdominal pain a few days ago, so he was admitted to the Pediatric Department at Masan Yangdeok Seoul Children's Hospital and is currently receiving inpatient treatment. I visited today. The hospital has inpatient rooms, good facilities, and friendly staff. The pediatric specialists are excellent, making it a well-known pediatric hospital, so I recommend it.