A radio communication apparatus comprising: an encoding section that performs channel coding on transmission data; a modulating section that modulates the channel coded transmission data using a modulation scheme determined by a determining section and generates a first modulated signal; a modulation diversity processing section that generates a second modulated signal from the generated first modulated signal, according to a determination by the determining section, the modulation diversity processing section comprising; a phase rotating section that rotates a phase of the first modulated signal; an IQ separating section that separates the rotated first modulated signal into an Ich component and a Qch component; an interleaver that performs an interleaving processing on one of the Ich component and the Qch component; and an IQ combining section that combines the Ich component and the Qch component after the interleaving processing, to generate the second modulated signal; a transmitting section (133, 134, 135) that generates a transmission signal from one of the first modulated signal and the second modulated signal, according to the determination by the determining section, and radio transmits the generated transmission signal; and the determining section that determines the modulation scheme from a plurality of modulation schemes for modulating the transmission data at the modulating section, whether the second modulated signal is to be generated, and whether the transmission signal is to be generated from the first modulated signal or the second modulated signal at the transmitting section (133, 134, 135) according to a finding of an interval in which a reception quality indicating a channel environment of the transmission signal fits in a sequence of intervals defined by a plurality of threshold values on a reception quality axis, wherein a modulation scheme of a higher level is assigned to one or two intervals containing higher reception quality values than one or two intervals corresponding to a modulation scheme of a lower level, and threshold values from the plurality of threshold values set boundaries for intervals corresponding to same modulation schemes, the transmission signal is generated from the second modulated signal if said reception quality is found in an interval with higher reception quality values from intervals corresponding to a same modulation scheme, and the transmission signal is generated from the first modulated signal if said reception quality is found in an interval with lower reception quality values from intervals corresponding to a same modulation scheme. an encoding section that performs channel coding on transmission data; a modulating section that modulates the channel coded transmission data using a modulation scheme determined by a determining section and generates a first modulated signal; a modulation diversity processing section that generates a second modulated signal from the generated first modulated signal, according to a determination by the determining section, the modulation diversity processing section comprising; a phase rotating section that rotates a phase of the first modulated signal; an IQ separating section that separates the rotated first modulated signal into an Ich component and a Qch component; an interleaver that performs an interleaving processing on one of the Ich component and the Qch component; and an IQ combining section that combines the Ich component and the Qch component after the interleaving processing, to generate the second modulated signal; a transmitting section (133, 134, 135) that generates a transmission signal from one of the first modulated signal and the second modulated signal, according to the determination by the determining section, and radio transmits the generated transmission signal; and the determining section that determines the modulation scheme from a plurality of modulation schemes for modulating the transmission data at the modulating section, whether the second modulated signal is to be generated, and whether the transmission signal is to be generated from the first modulated signal or the second modulated signal at the transmitting section (133, 134, 135) according to a finding of an interval in which a reception quality indicating a channel environment of the transmission signal fits in a sequence of intervals defined by a plurality of threshold values on a reception quality axis, wherein a modulation scheme of a higher level is assigned to one or two intervals containing higher reception quality values than one or two intervals corresponding to a modulation scheme of a lower level, and threshold values from the plurality of threshold values set boundaries for intervals corresponding to same modulation schemes, the transmission signal is generated from the second modulated signal if said reception quality is found in an interval with higher reception quality values from intervals corresponding to a same modulation scheme, and the transmission signal is generated from the first modulated signal if said reception quality is found in an interval with lower reception quality values from intervals corresponding to a same modulation scheme.