They will each collect a share in the region of £4 million pounds after their numbers came up in the National Lottery draw on 3 November.
Five of the group of women aged between 37 and 73 decided to resign after discovering they had won, with the oldest of the syndicate, Jean Cairns, having already retired.
All had worked as either catering assistants or catering supervisors at the hospital in Wales for at least the last 12 years.
Syndicate leader Julie Saunders, 56, told the BBC: "I've enjoyed working there for many years along with the rest of the syndicate, but now it is someone else's turn to take on those roles.
"We will miss many of our colleagues as we have all worked there a long time but it is the start of something new for us all."