PURPOSE: To efficiently carry out electroless gold plating on a copper base by adding potassium cyanide as a complexing agent to an electroless gold plating soln. contg. tartaric acid as a reducing agent and using the plating soln. after heating.

CONSTITUTION: Potassium cyanide as a complexing agent is added to an electroless gold plating soln. contg. tartaric acid as a reducing agent. The proper amt. of the cyanide added is about 0.8-3.0g/l. In the plating soln., free cyanogen accelerates the dissolution of a base metal and enables plating at a higher rate. When the electroless gold plating soln. contg. the added potassium cyanide is heated and used, the rate of gold plating by substitution on a copper base is increased to that on a nickel base and gold plating by substitution is simultaneously and efficiently carried out on both the bases.