This paper shows the degree of congestion at a restaurant in a theme park through a simulation using Little’s formula, which is the most basic principle in Queueing Theory. In a certain type of restaurant, customers place their orders and pay first, then stand in line to receive their meals. The problem is the long time needed to serve the meals even when vacant seats can easily be found. Regarding congestion, it takes 40 minutes or more for the customers to receive their orders after lining up in the restaurant. The purpose of this paper is to demonstrate a case where Little’s formula reproduces a real system.