Recently, there is a remarkable growth in IP broadcast services. There are time-based and flat-rate pricing methods, and there are issues obtaining the optimal viewing price depending on the pricing methods and services provided. An optimal viewing price should exist for IP broadcast services based on several viewpoints such as maximizing the revenue of IP broadcast service provider, maximizing network efficiency, maximizing user's utility, etc. The purpose of this paper is to clarify the optimal viewing price based on maximizing the revenue of IP broadcast service provider. Two kinds of pricing methods, time-based pricing and flat-rate pricing, and three kinds of price elasticity are considered for VOD type IP broadcast service. The relation between revenue and viewing price for each method and each price elasticity are shown. From simulation results, the optimal viewing price that maximizes the revenue of IP broadcast service provider is obtained.