Abstract: Provided is a sensitizing solution for electroless plating which can easily dissolve an Sn compound therein without the use of acid, and thus can be used for a long period of time without impairing the uniformity of a metal plating coating. The sensitizing solution for electroless plating is a sensitizing solution for electroless plating including: an Sn compound; and a solvent, wherein the solvent contains 10 vol. % or more of a water-soluble alcohol. In addition, provided is an electroless plating method including: a pretreatment process of immersing a body to be plated into a pretreatment solution; and a plating process of immersing the body to be plated after being subjected to the pretreatment process into a plating solution, wherein the sensitizing solution for electroless plating according to the invention is used as the pretreatment solution.