A mobile station apparatus which performs communication with a base station apparatus using enhanced physical downlink control channels, each of the enhanced physical downlink control channels being constituted of one or more first elements, the mobile station apparatus comprising: a radio resource control unit configured to obtain, from the base station apparatus, information for configuring a first enhanced physical downlink control channel region and a second enhanced physical downlink control channel region, and to configure, based on the information, the first enhanced physical downlink control channel region to which a first physical resource mapping is applied and the second enhanced physical downlink control channel region to which a second physical resource mapping is applied, wherein the first enhanced physical downlink control channel region is constituted of a plurality of physical resource block pairs within a downlink system band, the second enhanced physical downlink control channel region is constituted of a plurality of physical resource block pairs within the downlink system band, a first element is a minimum unit of resources used in configuration of an enhanced physical downlink control channel, for the first physical resource mapping, each of the first elements is constituted of a plurality of resources in one physical resource block pair, for the second physical resource mapping, each of the first elements is constituted of a plurality of second elements which are obtained by dividing resources capable of being used for a signal of the enhanced physical downlink control channel in each of the plurality of physical resource block pairs constituting the second enhanced physical downlink control channel region, one of the plurality of second elements is constituted of a plurality of resources in one of the different physical resource block pairs, and another one of the plurality of second elements is constituted of a plurality of resources in another one of the different physical resource block pairs; and a control unit configured to set a first search space for performing decoding detection of an enhanced physical downlink control channel within the first enhanced physical downlink control channel region and a second search space for performing decoding detection of an enhanced physical downlink control channel within the second enhanced physical downlink control channel region; and a reception processing unit configured to perform decoding detection of the enhanced physical downlink control channel within the first search space and the enhanced physical downlink control channel within the second search space. a radio resource control unit configured to obtain, from the base station apparatus, information for configuring a first enhanced physical downlink control channel region and a second enhanced physical downlink control channel region, and to configure, based on the information, the first enhanced physical downlink control channel region to which a first physical resource mapping is applied and the second enhanced physical downlink control channel region to which a second physical resource mapping is applied, wherein the first enhanced physical downlink control channel region is constituted of a plurality of physical resource block pairs within a downlink system band, the second enhanced physical downlink control channel region is constituted of a plurality of physical resource block pairs within the downlink system band, a first element is a minimum unit of resources used in configuration of an enhanced physical downlink control channel, for the first physical resource mapping, each of the first elements is constituted of a plurality of resources in one physical resource block pair, for the second physical resource mapping, each of the first elements is constituted of a plurality of second elements which are obtained by dividing resources capable of being used for a signal of the enhanced physical downlink control channel in each of the plurality of physical resource block pairs constituting the second enhanced physical downlink control channel region, one of the plurality of second elements is constituted of a plurality of resources in one of the different physical resource block pairs, and another one of the plurality of second elements is constituted of a plurality of resources in another one of the different physical resource block pairs; and a control unit configured to set a first search space for performing decoding detection of an enhanced physical downlink control channel within the first enhanced physical downlink control channel region and a second search space for performing decoding detection of an enhanced physical downlink control channel within the second enhanced physical downlink control channel region; and a reception processing unit configured to perform decoding detection of the enhanced physical downlink control channel within the first search space and the enhanced physical downlink control channel within the second search space.