The present invention relates to a deaerator 2 including: a liquid flow space; reduced-pressure spaces 25A, 25B, and 25C; gas permeable films 21A, 21B, and 21C that separate these spaces; and a pump for discharging gas from within the reduced-pressure spaces 25A, 25B, and 25C to the outside, and to a liquid chromatograph equipped with the deaerator 2. The deaerator 2 further includes gas partial pressure variation suppression means 23A, 23B, 23C, 25Ab, 25Bb, 25Cb, 29A, 29B, and 29C for suppressing variations in partial pressures of a specific gas in the reduced-pressure spaces 25A, 25B, and 25C.