Decomposing/cleaning composition, method for cleaning adhesive polymer, and method for producing device wafer

A decomposing cleaning composition of an adhesive polymer comprising a quaternary alkylammonium fluoride or a hydrate of a quaternary alkylammonium fluoride, and an aprotic solvent, wherein the aprotic solvent comprises

• (A) an N-substituted amide compound having no active hydrogen on a nitrogen atom, and
• (B) at least one organic sulfur oxide selected from the group consisting of a sulfoxide compound and a sulfone compound,
• the content of the (A) N-substituted amide compound is 30 to 99% by mass and the content of the (B) organic sulfur oxide is 1 to 70% by mass, with respect to 100% by mass of the aprotic solvent,
• the content of the quaternary alkylammonium fluoride is 0.1 to 15% by mass,
• the (A) N-substituted amide compound is at least one selected from the group consisting of N-methylpyrrolidone, N-ethylpyrrolidone, and 1,3-dimethyl-2-imidazolidinone,
• the (B) organic sulfur oxide is at least one selected from the group consisting of dimethyl sulfoxide and sulfolane, and
• the quaternary alkylammonium fluoride is tetrabutylammonium fluoride.