Pretreatment method for electroless plating, and pretreatment solution for electroless plating

The present invention provides a pretreatment method for electroless plating and a pretreatment solution for electroless plating, both of which make it possible to increase the amount of a catalyst adsorbed. A pretreatment method for electroless plating, comprising at least a cleaner step S10, a soft etching step S20 and/or an acid treatment step S30, a catalyst application step S40 and a catalyst reduction step S50, and enabling electroless plating on a substrate, the pretreatment method being characterized in that an anionic surfactant of which a hydrophilic group moiety can be ionized into an anion is added to a treatment solution to be used in the soft etching step S20 and/or the acid treatment step S30, an ionic catalyst is applied onto the substrate in the catalyst application step S40, and the ionic catalyst is reduced to increase the amount of the catalyst adsorbed onto the substrate in the catalyst reduction step S50.