A transmission apparatus according to the present invention includes: a baseband signal generator; a local oscillator; a modulator that generates a modulation signal by multiplying a baseband signal by a carrier wave signal including a local oscillation frequency; a power amplifier that amplifies the modulation signal; a filter having a pass bandwidth that is narrower than a frequency bandwidth that can be set or emerge in the local oscillator and removes at least a part of unwanted component generated in association with the modulation signal that is amplified; and a frequency bandwidth inside/outside decision unit that decides that the local oscillation frequency is out of a predetermined bandwidth. The transmission apparatus controls one of the baseband signal generator and the local oscillator to reduce the modulation signal when it is decided by the frequency bandwidth inside/outside decision unit that the local oscillation frequency is out of the predetermined bandwidth.