An immersion solution for a microscope, the immersion solution including a metal-halogeno complex anion containing bromine or iodine and one or more types of metal elements M selected from Sn, In, Bi, Sb, Zn and Al, and an imidazolium cation, a pyridinium cation, a pyrrolidinium cation or an ammonium cation. The immersion solution includes an ionic liquid that transmits light having a predetermined wavelength, has a refractive index of no less than 1.60 and is used for a fluorescence microscope.