A signal processing circuit performs processing for an analog signal output from a head. The signal processing circuit includes: a conversion section that generates a digital signal based on the analog signal; a first filter that equalizes the output of the conversion section; a demodulation section that demodulates data from the output of the first filter; a modulation section that modulates a waveform based on the data demodulated by the demodulation section; a second filter that equalizes the output of the modulation section; and an adaptation section that adapts the response of the second filter such that the output of the second filter becomes equal to the output of the conversion section.