The invention discloses a paper double-sided sizing device and a sizing method. The paper double-sided sizing device comprises a glue tray, a first scraper bar, a second scraper bar, a displacement adjusting mechanism and an operating mechanism. The first scraper bar and the second scraper bar are disposed above the glue tray and the displacement adjustment mechanism adjusts the distance between the first scraper bar and the second scraper bar to a first distance or a second distance. Glue for immersing a paper to be sized is arranged in the glue tray. The operating mechanism feeds one end of the impregnated paper to a position between the first scraper bar and the second scraper bar and drives one end of the paper to move away from the glue tray. The first scraper bar scrapes glue on one surface of the paper and the second scraper bar scrapes glue on the other surface of the paper. The method realizes uniform double-sided sizing, can control a sizing amount, solves the problem that the surface sizing in the laboratory is uneven, ensures the reliability of the data and produces positive effects on application and analysis of a sized chemical product of paper making.