The purpose of the present invention is to provide a processing solution and a processing method which, when applied to a laminate body including an InP layer and an SiO2 layer formed on the InP layer, enables selectively removing the SiO2 layer and can suppress defects in the SiO2 layer and surface roughness of the InP layer. The invention is of a processing method and a processing solution which contains hydrogen fluoride and an anti-corrosive agent, wherein the number of coarse particles with a particle size greater than or equal to 0.10 [mu]m per 1 mL of the processing solution is less than 100 particles/mL, the number of coarse particles with a particle size greater than or equal to 0.05 [mu]m per 1 mL of the processing solution is less than 500 particles/mL, and the value of the ratio of the number of coarse particles with a particle size greater than or equal to 0.10 [mu]m per 1 mL of the processing solution to the number of coarse particles with a particle size greater than or equal to 0.05 [mu]m per 1 mL of the processing solution is greater than 0.010 and less than 1.000.