The central Visby town house on the Baltic Sea island of Gotland was built in 1750 on the foundations of a Russian church. The kitchen lies on the presbytery, and the tomb containing the skeleton - visible through a glass panel - is in the cellar.
The real estate agency's owner Leif Bertwig says there is no reason to be afraid as the skeleton "lies in consecrated soil and rests in peace."
Bertwig said Wednesday the remains likely belong to a Russian man who died some 800 years ago.
The starting price for the house - all included - is 4.1 million kronor ($640,000).