Provided is a modulation device which generates a phase modulation signal and an amplitude modulation signal and can correct an I/Q orthogonal shift and reduce degradation of the ON/OFF ratio. In the device, a phase shifter (174) controls voltage applied to a capacitor in accordance with a control signal outputted from a phase control unit (180) and adjusts the capacitance so as to shift the phase of a carrier generated by an oscillator (173). The phase control unit (180) estimates a phase shift of a phase shifter (174) in accordance with an output RF signal (S140) by using the phase shift estimation method. Furthermore, the phase control unit (180) performs tuning of the phase shifter (174) according to the estimated value of the phase shift of the phase shifter (174) so that a phase difference between carries of an I signal (S125) and a Q signal (S135) is 90 degrees.