A radio communication base station device which can reduce the number of judgment times for a control signal in a mobile station, thereby suppressing power consumption by the mobile station. The radio communication base station device (100) includes: a mapping setting unit (122) which sets a mapping method in a mapping unit (102); the mapping unit (102) which maps a control signal to respective mobile stations to any of sub carriers constituting the OFDM symbol according to the mapping method set by the mapping setting unit (122); an MCS setting unit (121) which references a mapping table in which correlation between a plurality of MCS having different MCS levels and mapping methods is set according to the judgment result of the mapping setting unit (122) and sets MCS in encoding/modulation units (101-1 to 101-n).