An EPDCCH is made up of an aggregation of one or more resources obtained by dividing one of PRB pairs. In a case where a total number of antenna ports for transmitting reference signals to be used to demodulate signals mapped to the EPDCCH is four, four resources obtained by dividing one of the PRB pairs correspond to the antenna ports of different numbers. In a case where a total number of antenna ports for transmitting reference signals to be used to demodulate signals mapped to the EPDCCH is two, two resources obtained by dividing one of the PRB pairs correspond to the antenna ports of different numbers. A mobile station apparatus includes a reception processor that demodulates, by using reference signals transmitted from the antenna ports corresponding to the resources used for the EPDCCH, signal mapped to the EPDCCH for which decoding and detection are performed.