PURPOSE: To improve its cleaning power and to reduce influences on metals, resins and rubber by adding a specified Quantity of 1, 2 dichloro-1-fluoroethane and nitromethane.

CONSTITUTION: A flux cleaning agent is composed of 94W100% 1,2 dichloro-1- fluoroethane and 0W6% nitromethane. By this composition, the capacity of removing flux from substrates of electric and electronic circuit improves remarkably, and at the same time, eliminates rusting of metals of circuit substrate and adverse influences such as swelling etc. on rubber and resin. Accordingly, the cleaning capacity for flux can be improved by this method, and at the same time, influences on synthetic resin and rubber can be decreased.