The fourth flight of the Epsilon launch vehicle was successfully conducted in January, 2019. The Epsilon successfully delivered a total of seven satellites into Sun Synchronous Orbit (SSO) as its first rideshare mission. In order to correspond to this mission, a new Guidance and Control (GC) system was developed. This paper first introduces the outline of GC system of the Epsilon. Then, we describe newly developed GC system for the rideshare option. Finally, we describe the flight result of the fourth Epsilon.