Among flocculating agents reacting in a neutral region and also leaving treated water also in neutral region, a flocculating agent is proposed, which can be used simply and may carry out effective cleaning of mud water in particular.A flocculating agent is proposed, which is a flocculating agent in powder form and exhibiting a pH of 5 to 9 when added to pure water, containing in a mixed state an acidic powder comprising porous particles obtained by adsorbing a metal constituent and an alkaline powder comprising porous particles obtained by adsorbing calcium phosphate.