A reception apparatus comprising: receiving means for coherently detecting, based on local light, an optical signal containing modulated light and pilot light, and outputting an electrical signal containing a modulated signal corresponding to the modulated light and a pilot signal corresponding to the pilot light; first discrete Fourier transform means for performing a discrete Fourier transform on first time samples obtained by sampling the electrical signal output by the receiving means at a first sampling rate, and outputting first frequency samples of the electrical signal; first compensating means for detecting a first frequency of the pilot signal based on the first frequency samples, determining and compensating for first frequency error in the electrical signal based on error in the first frequency of the pilot signal relative to a reference frequency; first filter means for processing the first frequency samples from the first compensating means to filter out the pilot signal, and outputting second frequency samples corresponding to the modulated signal; first discrete inverse Fourier transform means for performing a discrete inverse Fourier transform on the second frequency samples corresponding to the modulated signal, and outputting second time samples corresponding to the modulated signal; second filter means for processing the first frequency samples from first compensating means to filter out the modulated signal, and outputting third frequency samples corresponding to the pilot signal; frequency converting means for processing the third frequency samples to convert the frequency of the pilot signal to be lowered by the reference frequency, and outputting fourth frequency samples corresponding to the pilot signal; converting means (19, 20, 22, 23) for converting the fourth frequency samples corresponding to the pilot signal to the third time samples at a second sampling rate by downsampling and discrete inverse Fourier transforming on the fourth frequency samples corresponding to the pilot signal; second discrete Fourier transform means for performing a discrete Fourier transform on the third time samples, and outputting fifth frequency samples corresponding to the pilot signal; and second compensating means for determining a second frequency error in the modulated signal by detecting a frequency of the pilot signal based on the fifth frequency samples, and compensating for the second frequency error in the modulated signal from the first discrete inverse Fourier transform means, wherein the reference frequency is a frequency of one sample of the first frequency samples output by the first discrete Fourier transform means. receiving means for coherently detecting, based on local light, an optical signal containing modulated light and pilot light, and outputting an electrical signal containing a modulated signal corresponding to the modulated light and a pilot signal corresponding to the pilot light; first discrete Fourier transform means for performing a discrete Fourier transform on first time samples obtained by sampling the electrical signal output by the receiving means at a first sampling rate, and outputting first frequency samples of the electrical signal; first compensating means for detecting a first frequency of the pilot signal based on the first frequency samples, determining and compensating for first frequency error in the electrical signal based on error in the first frequency of the pilot signal relative to a reference frequency; first filter means for processing the first frequency samples from the first compensating means to filter out the pilot signal, and outputting second frequency samples corresponding to the modulated signal; first discrete inverse Fourier transform means for performing a discrete inverse Fourier transform on the second frequency samples corresponding to the modulated signal, and outputting second time samples corresponding to the modulated signal; second filter means for processing the first frequency samples from first compensating means to filter out the modulated signal, and outputting third frequency samples corresponding to the pilot signal; frequency converting means for processing the third frequency samples to convert the frequency of the pilot signal to be lowered by the reference frequency, and outputting fourth frequency samples corresponding to the pilot signal; converting means (19, 20, 22, 23) for converting the fourth frequency samples corresponding to the pilot signal to the third time samples at a second sampling rate by downsampling and discrete inverse Fourier transforming on the fourth frequency samples corresponding to the pilot signal; second discrete Fourier transform means for performing a discrete Fourier transform on the third time samples, and outputting fifth frequency samples corresponding to the pilot signal; and second compensating means for determining a second frequency error in the modulated signal by detecting a frequency of the pilot signal based on the fifth frequency samples, and compensating for the second frequency error in the modulated signal from the first discrete inverse Fourier transform means, wherein the reference frequency is a frequency of one sample of the first frequency samples output by the first discrete Fourier transform means.