A communication apparatus has a local oscillator which performs phase modulation based on a phase component of a baseband signal and outputs a phase modulated signal, a controlling circuit which is supplied with an integer portion included in an amplitude component of the baseband signal and generates and outputs a controlling signal based on a size of the integer portion, a subtractor which is supplied with the integer portion and the controlling signal, subtracts a value of the controlling signal from the integer portion, and outputs a result, a MASH (Multi-stAge-noise-Shaping) circuit which is a second-order delta-sigma modulation means supplied with a fractional portion of the amplitude component, an order of the MASH circuit being switchable between a first order and a second order based on the controlling signal, and an amplifier which sets a voltage value based on an output of the MASH circuit and an output of the subtractor, multiplies the voltage value and the phase modulated signal, and outputs a result.