The present invention provides a method of purifying RNA, including contacting a solid support with an acidic solution having a RNA-containing sample and a kosmotropic salt having a concentration of less than 1M, thereby binding the RNA to the solid support. According to the present invention, RNA is purified efficiently due to high RNA yield and low contamination by DNA. The present invention is particularly effective in purifying RNAs of 200 nucleotides or less.