Sludge dehydrating agent and sludge dehydration method

A sludge dehydrating agent with a polymer which has a constituent unit derived from a cationic monomer,

• wherein a value k determined from an intrinsic viscosity [η]1[dL/g] of a 1-mol/L aqueous sodium nitrate solution of the polymer at 30° C. and an intrinsic viscosity [η]0.01 [dL/g] of a 0.01-mol/L aqueous sodium nitrate solution of the polymer at 30° C. in accordance with formula (I) is 0.8 to 2.2 exclusive,
• k=([η]0.01−[η]1)/9 (I),
• wherein the intrinsic viscosity [η] 1 is 1.0 to 6.5 dL/g, and the intrinsic viscosity [η]0.01 is 8.5 to 26.0 dL/g,
• wherein the sludge dehydrating agent contains a polymer having the K value, wherein the k value is adopted as a parameter based on an intrinsic viscosity of the polymer which correlates with a degree of spread or contraction of a polymer chain.