A mobile station apparatus of a mobile communication system including a base station apparatus and the mobile station apparatus, wherein the mobile station apparatus is characterized in that: the mobile station apparatus comprises a wireless section and a radio resource control section, wherein the wireless section is configured to: communicate with the base station apparatus by carrier aggregation using a plurality of component carriers including a first component carrier and one or more second component carriers, and receive system information from the base station apparatus; the radio resource control section is configured to: use first system information respectively for each component carrier, and use second system information commonly for all component carriers, wherein the first system information and the second system information are the system information received from the base station apparatus; and the wireless section is further configured to: receive, from the base station apparatus, a wireless signal including a paging channel which is transmitted on the first component carrier, the paging channel being used to notify the mobile station apparatus of updating system information broadcasted on the first component carrier, update the system information broadcasted on the first component carrier in a case where updating system information is notified via the paging channel, and receive, from the base station apparatus, system information which are specific to the second component carrier via radio resource control signaling. the mobile station apparatus comprises a wireless section and a radio resource control section, wherein the wireless section is configured to: communicate with the base station apparatus by carrier aggregation using a plurality of component carriers including a first component carrier and one or more second component carriers, and receive system information from the base station apparatus; the radio resource control section is configured to: use first system information respectively for each component carrier, and use second system information commonly for all component carriers, wherein the first system information and the second system information are the system information received from the base station apparatus; and the wireless section is further configured to: receive, from the base station apparatus, a wireless signal including a paging channel which is transmitted on the first component carrier, the paging channel being used to notify the mobile station apparatus of updating system information broadcasted on the first component carrier, update the system information broadcasted on the first component carrier in a case where updating system information is notified via the paging channel, and receive, from the base station apparatus, system information which are specific to the second component carrier via radio resource control signaling. use first system information respectively for each component carrier, and use second system information commonly for all component carriers, wherein the first system information and the second system information are the system information received from the base station apparatus; and the wireless section is further configured to: receive, from the base station apparatus, a wireless signal including a paging channel which is transmitted on the first component carrier, the paging channel being used to notify the mobile station apparatus of updating system information broadcasted on the first component carrier, update the system information broadcasted on the first component carrier in a case where updating system information is notified via the paging channel, and receive, from the base station apparatus, system information which are specific to the second component carrier via radio resource control signaling. receive, from the base station apparatus, a wireless signal including a paging channel which is transmitted on the first component carrier, the paging channel being used to notify the mobile station apparatus of updating system information broadcasted on the first component carrier, update the system information broadcasted on the first component carrier in a case where updating system information is notified via the paging channel, and receive, from the base station apparatus, system information which are specific to the second component carrier via radio resource control signaling.