A radio communication system comprising: a first radio communication apparatus and a second radio communication apparatus that communicate by radio with each other using a plurality of component carriers; wherein the first radio communication apparatus includes: a control unit configured to specify a radio resource area in which the second radio communication apparatus searches for a control signal based on a subframe number associated with the control signal transmitted by the first radio communication apparatus, an identifier assigned to the second radio communication apparatus and information about the plurality of component carriers; and a transmitting unit configured to transmit the control signal addressed to the second radio communication apparatus, in the radio resource area specified by the control unit; and wherein the second radio communication apparatus includes: a calculating unit configured to calculate the specified radio resource area, based on the subframe number associated with the control signal transmitted by the first radio communication apparatus, the identifier assigned to the second radio communication apparatus and the information about the plurality of component carriers; and a detecting unit configured to search signals in the radio resource area calculated by the calculating unit, out of signals received from the first radio communication apparatus, so as to detect the control signal addressed to the second radio communication apparatus, wherein the radio resource area in which the second radio communication apparatus searches for the control signal is determined by inputting numerical values including: a component carrier number and the identifier assigned to the second radio communication apparatus into a predetermined function. a first radio communication apparatus and a second radio communication apparatus that communicate by radio with each other using a plurality of component carriers; wherein the first radio communication apparatus includes: a control unit configured to specify a radio resource area in which the second radio communication apparatus searches for a control signal based on a subframe number associated with the control signal transmitted by the first radio communication apparatus, an identifier assigned to the second radio communication apparatus and information about the plurality of component carriers; and a transmitting unit configured to transmit the control signal addressed to the second radio communication apparatus, in the radio resource area specified by the control unit; and a control unit configured to specify a radio resource area in which the second radio communication apparatus searches for a control signal based on a subframe number associated with the control signal transmitted by the first radio communication apparatus, an identifier assigned to the second radio communication apparatus and information about the plurality of component carriers; and a transmitting unit configured to transmit the control signal addressed to the second radio communication apparatus, in the radio resource area specified by the control unit; and wherein the second radio communication apparatus includes: a calculating unit configured to calculate the specified radio resource area, based on the subframe number associated with the control signal transmitted by the first radio communication apparatus, the identifier assigned to the second radio communication apparatus and the information about the plurality of component carriers; and a detecting unit configured to search signals in the radio resource area calculated by the calculating unit, out of signals received from the first radio communication apparatus, so as to detect the control signal addressed to the second radio communication apparatus, wherein a calculating unit configured to calculate the specified radio resource area, based on the subframe number associated with the control signal transmitted by the first radio communication apparatus, the identifier assigned to the second radio communication apparatus and the information about the plurality of component carriers; and a detecting unit configured to search signals in the radio resource area calculated by the calculating unit, out of signals received from the first radio communication apparatus, so as to detect the control signal addressed to the second radio communication apparatus, wherein the radio resource area in which the second radio communication apparatus searches for the control signal is determined by inputting numerical values including: a component carrier number and the identifier assigned to the second radio communication apparatus into a predetermined function.