A radio communication device using a quadrature modulation-demodulation circuit which enables DC offset error fluctuation to be corrected more accurately regardless of the condition of temperature variation or power source voltage fluctuation. A quadrature demodulation circuit inputs therein a QPSK signal to output a base band signal perpendicularly intersecting to the QPSK signal. A base band signal generation circuit inputs therein a transmission data to convert into two analog base band signals perpendicularly intersecting with each other. A quadrature modulation circuit inputs therein the analog base band signal and modulated frequency signal to output the QPSK signal. A switching circuit selects either one of the analog base band signal and the QPSK signal. An A/D conversion circuit quantizes an output signal of the switching circuit. An offset error detecting means detects DC offset error. Consequently, the radio communication device causes the DC offset error caused by temperature variation and power source voltage fluctuation to be reduced regardless of on operation.