The Grade II-listed Lion Salt Works, near Northwich, produced salt since its opening in 1894 but closed in 1986.
A four-year project used traditional construction skills and most of the original building material, Cheshire West and Chester Council said.
It added the museum, which also has a butterfly conservation area, aims to be "a valued resource" locally.
The restoration received a £5.3m grant from the Heritage Lottery Fund and £3m from the site's current owners Cheshire West and Chester Council.
Lion Salt Works also featured on the BBC's Restoration programme in 2004, attracting more than 32,000 votes, but missed out on a place in the competition's final.
It is one of four historic open-pan salt-making sites in the world.
Source: Cheshire West and Chester Council
A former Cheshire salt works has reopened to the public as a museum after a £10.2m restoration.