Where is the oldest continuously operated cheese maker in the world?

Marin French Cheese Company is the oldest in Usa since 1865
http://www.marinfrenchcheese.com/

Steiner Cheese, founded in 1833, claims to be the oldest continuously operating cheese manufacturer in the USA.

http://www.cheesereporter.com/i/content/pdfs/Steiner%20Cheese.pdf

Then again, this source suggests that the first cheese factory wasn't established until 1851.

https://en.wikipedia.org/wiki/Cheese#History

Of course, this assumes you are talking about industrial production. There could well be an English dairy farm that has been producing cheese for local consumption for much longer than that!

The producers of Roquefort were given a monopoly in 1411, but the cheese production there goes back long before, being mentioned in 79CE (and prehistoric evidence of cheese production is alleged to have been found too). https://en.wikipedia.org/wiki/Roquefort This isn't a company, as companies in the modern sense didn't exist then.