11:00 - 21:30 everyday, except new yearday, seolnal
I don't know the hours. I am sure you can ask your hotel once you check in to phone the restaurant. We were there around 11:45 on a week day, it fills up very quickly by noon.
Get quick answers from Hwangsaengga Kalguksu staff and past visitors.
3 Days in Seoul
Guide to Seoul Outdoors
Guide to Seoul for Families