To provide an organic sludge dehydrating method of leaving the merit of a crosslinkable water soluble ionic polymer and solving not only the problem of a reduction in addition amount but also the problem of a product solubility or an environmental effect.

In the organic sludge dehydrating method, an amphoteric water-soluble polymer (A) of which the cation equivalent value is equal to or higher than an anion equivalent value and an amphoteric water soluble polymer (B) of which the anion equivalent value is higher than the cation equivalent value, which comprises a dispersion prepared by a dispersion polymerization method for polymerizing a water-soluble monomer containing a cationic monomer and an anionic monomer as essential components in a salt aqueous solution in the coexistence of a high-molecular dispersant soluble in the salt aqueous solution to form polymer particles with a particle size of 100 μm or below insoluble in the salt aqueous solution, are combined with each other and added to organic sludge to dehydrate the organic sludge.