Ronald Perley, 52, was taken into custody for the alleged theft at Bellman's Jewelers, WMUR-TV, Manchester, N.H., reported.
Employees at the store called police Thursday to report they witnessed Perley attempt to steal the ring.
The employees told police Perley entered the store and asked to see several engagement rings. While looking at a ring, Perley allegedly made a run for the door, police said.
Perley was unable to exit the store because, as a precaution, the store's door is kept locked from the inside. When confronted by employees at the store, Perley allegedly swallowed the ring.
When police arrived at the scene, Perley denied the attempted theft. He was taken into custody and held until police obtained a search warrant.
He was then taken to a hospital, where an X-ray showed a ring was inside his body, police said.
Surveillance video from the store allegedly showed Perley attempting to steal, then swallowing the ring.
Perley was charged with felony theft and falsifying physical evidence. He was granted $50,000 bail on the condition that he not be released until he passed the ring.
WMUR-TV reported Saturday police have recovered the ring.