When communication of a type, such as a priority call, to be prioritized over a normal call has occurred, appropriate measurement of CSG cells is performed. There is provided a mobile station apparatus applied to a mobile communication system that includes a small base station apparatus which makes only mobile station apparatuses registered in advance accessible in normal case, and on the other hand, makes unregistered mobile station apparatuses accessible in non-normal case, wherein the mobile station apparatus is provided with at least: a cell information management section 103 that outputs cell type determination information for distinguishing a normal base station apparatus from a small base station apparatus; and a reception signal processing section 102 that selects whether or not to perform measurement of a channel state between the mobile station apparatus and the small base station apparatus, based on cell type determination information and access-class information indicating a priority of communication, and performs measurement of the channel state according to the selection result.