Provided is a cleaning agent for electronic materials, which enables very efficient advanced cleaning such that yield in the production of the electronic materials is improved and cleaning in a short period of time becomes possible, the cleaning agent having excellent cleaning power for fine-grained particles and organic matter and being able to reduce metallic contamination on the substrate. The cleaning agent for electronic materials comprises sulfamic acid (A), an anionic surfactant having at least one sulfonic acid group or a salt thereof in the molecule (B), a chelating agent (C), and water, wherein the pH at 25 C is preferably not more than 3.0 and the (B) is preferably a polymeric anionic surfactant (B1) having a weight average molecular weight of 1,000 to 2,000,000.