It's a very nice museum but I recommend you to spend not more than 30minutes there as it's not very big, couldn't be compared to other museums like in Olimpia or Delphi. However it's worth to see as they have many artifacts from ancient Corinth well presented there.
Before you even go there please also check the opening hours, cause they can be changed every day. Then you will be sure you won't travel for nothing to see only closed door.
The entrance fee (which includes also the museum) is 6 euros (3e reducted for children and students with ISIC card).
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.