PURPOSE: To provide a method of forming a thin film multilayer circuit having an insulating film which has no pin holes and geneates a lower degree of short- circuit and leak through vacuum evacuation in the third step.

CONSTITUTION: In the first step, a conductor 9 in formed on a substrate 8. In the second step, the conductor 9 is patterned. In the third step, the conductor 9 is coated with a polyimide resin solution and vacuum evacuation is carried out. In the fourth step, cure and via holes are bored. In the fifth step, a conductor is buried and above steps are then repeated to form a thin film multilayer circuit.