There is a concern that communication failure may occur in a case that the state of a serving cell is not properly managed during communication of SPS or GF. A mobile station apparatus of a communication system including at least a base station apparatus and a mobile station apparatus configured to perform communication by using carrier aggregation that simultaneously uses multiple serving cells configured by the base station apparatus according to an aspect of the present invention, wherein the mobile station apparatus restarts a deactivation timer of a serving cell of the multiple serving cells at a timing indicated by a configured uplink grant configured for the serving cell.