This invention intends to provide a polar modulating circuit, a polar modulating method, an integrated circuit and a radio transmission device capable of compensating for a delay difference between paths of a phase signal and an amplitude signal while suppressing an increase in the circuit scale in a polar modulating system. In a delay quantity determining unit 102, delay quantity information relative to the amplitude value of the amplitude signal or transmission level information S1, based on the step response characteristic of a power amplifying unit 105 are previously stored as table data. Thus, by executing delay adjustment using, as a reference signal, the amplitude signal or transmission level information S1, the delay difference between paths of a phase signal and an amplitude signal can be compensated for while suppressing an increase in the circuit scale.