A cleaning agent for a semiconductor substrate having a copper wiring film or a copper alloy wiring film, and a cobalt-containing film to be used in a post-process of a chemical mechanical polishing process, comprising an organic acid represented by general formula, amines selected from the group consisting of (B-1) diamines represented by general formula, (B-2) amidines represented by general formula, (B-3) azoles represented by general formula, and (B-4) pyrazines or pyrimidines represented by general formula, a hydroxylamine derivative, and an oxygen scavenger represented by general formula; and being an aqueous solution having a pH of 10 or higher: wherein R 1 represents a carboxyl group, a 1,2,3-trihydroxypropyl group or a 3-oxo-1,2-dihydroxypropyl group; wherein R 2 and R 3 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms, R 4 represents a hydrogen atom, a hydroxyl group or an alkyl group having 1 to 4 carbon atoms which may have a hydroxyl group, R 5 and R 6 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R 2 and R 3, R 3 and R 6, or R 4 and R 6 may form an alkylene chain having 1 to 3 carbon atoms, m represents 0 or 1, and n represents an integer of 0 to 2; wherein R 7 represents an alkyl group having 1 to 4 carbon atoms, R 8 represents an amino group, R 7 and R 8 may form an alkylene chain having 3 to 6 carbon atoms, R 9 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, T 1 represents a -CH 2 - group or a -C(=O)- group, and p represents 0 or 1; wherein R 10 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R 11 represents a hydrogen atom, a mercapto group, an amino group, an alkyl group having 1 to 4 carbon atoms or a 2-imidazolyl group, T 2 represents a nitrogen atom or a -C(-R 12)- group, wherein R 12 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, T 3 represents a nitrogen atom or a -C(-R 13)- group, wherein R 13 represents a hydrogen atom, a hydroxyl group or an alkyl group having 1 to 4 carbon atoms which may have an amino group, and T 4 represents a nitrogen atom or a -CH- group, provided that at least one of T 2 and T 4 represents a nitrogen atom; wherein R 14 to R 16 each independently represent a hydrogen atom, a hydroxyl group or an alkyl group having 1 to 4 carbon atoms which may have an amino group or a hydroxyl group, T 5 represents a nitrogen atom or a -C(-R 17)- group, wherein R 17 represents a hydrogen atom, a hydroxyl group or an alkyl group having 1 to 4 carbon atoms which may have an amino group or a hydroxyl group, and T 6 represents a nitrogen atom or a -C(-R 18)- group, wherein R 18 represents a hydrogen atom, a hydroxyl group or an alkyl group having 1 to 4 carbon atoms which may have an amino group or a hydroxyl group, provided that at least one of T 5 and T 6 represents a nitrogen atom; wherein R 19 represents a hydrogen atom or a hydroxyl group, R 20 represents a hydrogen atom or a hydroxyl group, R 21 represents a hydrogen atom, a hydroxyl group, a carboxyl group or a propoxycarbonyl group, provided that at least one of R 19 to R 21 represents a hydroxyl group, and wherein the hydroxylamine derivative is a hydroxylamine derivative represented by general formula: wherein R 22 represents an alkyl group having 1 to 6 carbon atoms, and R 23 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and wherein the alkyl group having 1 to 6 carbon atoms represented by R 22 and R 23 in general formula may be any of a straight chained, branched or cyclic group.