To provide an amphoteric polymer flocculant that, when being used in sludge dehydration treatment, achieves high strength of formed flock and high filtration rate and can sufficiently reduce a water content of an obtained dehydrated cake.

An amphoteric polymer flocculant includes: a polymer compound A having an anionic group and having a weight average molecular weight Mw of 1,000 to 1,000,000; and a polymer compound B having a cationic monomer unit. The polymer compound A is included by 0.1-10 pts.mass based on 100 pts.mass of the polymer compound B.