To provide a polymer flocculant having a high molecular weight and less water-insoluble components using a more general-purpose aqueous solution polymerization method.

There is provided a polymer flocculant (P) containing a water-soluble polymer (A) which is obtained by subjecting a polymerizable monomer (a) containing a water-soluble unsaturated monomer (a1) to aqueous solution polymerization in the presence of at least one radical generator (c) selected from the group consisting of a heat-decomposition type radical generator (c1) and an oxidation-reduction type radical generator (c2) and which satisfies the following relational expression (1), the polymer flocculant satisfying the following relational expression (2): 15≤[η]≤35 (1) and 0≤[I]≤10 (2).