Micromachining treatment agent and micromachining treatment method

Provided are a micromachining treatment agent and a micromachining treatment method with which it is possible to satisfactorily micromachine an object to be treated having at least a silicon-containing insulating film while suppressing the residue of fine particles. The micromachining treatment agent according to the present invention contains a compound represented by chemical formula (1), hydrogen fluoride, ammonium fluoride, and water, in the chemical formula (1) M + + (Rf-SO2)-N--(SO2-Rf), Rf represents a perfluoroalkyl group having 1-4 carbon atoms, M + represents a hydrogen ion or an ammonium ion, the content of the compound is 0.001-0.5 mass% with respect to the total mass of the micromachining treatment agent, and the content of the compound is 0.1-0.5 mass% with respect to the total mass of the micromachining treatment agent. The content of the hydrogen fluoride is 0.05-25 mass% with respect to the total mass of the micromachining treatment agent, the content of the ammonium fluoride is 0.5-40 mass%