It is an object of the present invention to provide a polyalkyleneimine alkyleneoxide copolymer, which is suitably used as a builders for a detergent, a detergent, a water treatment agent, a dispersant and the like and which can exert high basic performance in point of the detergency or the like, a production method thereof, and use thereof.The present invention is directed to a polyalkyleneimine alkyleneoxide copolymer comprising an alkyleneimine monomer unit having polyalkyleneoxide,wherein the polyalkyleneoxide has an end structure containing at least one selected from the group consisting of: (1) --CO--R.sup.2--COOX; (2) --CH.sub.2CH(OH)--R.sup.3; (3) --CH.sub.2CH(OH)CH.sub.2--O--R.sup.4; and (4) --C(O)--NH--R.sup.5, wherein R.sup.2 represents an alkylene group having 2 to 8 carbon atoms, an alkenylene group having 2 to 8 carbon atoms, an arylene group having 6 to 14 carbon atoms or a sulfoalkylene group having 2 to 8 carbon atoms; R.sup.3 represents an alkenyl group having 2 to 6 carbon atoms, an aryl group having 6 to 14 carbon atoms, a sulfoalkyl group having 2 to 6 carbon atoms or a hydroxyalkyl group having 2 to 6 carbon atoms; R.sup.4 represents a hydrogen atom, an alkyl group having 2 to 8 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group having 6 to 14 carbon atoms or a sulfoalkyl group having 2 to 6 carbon atoms; R.sup.5 represents an alkyl group having 2 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms or a sulfoalkyl group having 2 to 6 carbon atoms; and X represents a hydrogen atom, an alkaline metal atom, an alkaline earth metal atom, an ammonium group or an organic ammonium group.