A thin film of a preselected compound having a large area is continuously produced on a substrate by depositing elements constituting the preselected compound from a target member onto the surface of a substrate by sputtering, comprising the steps of:rotating a first target member having a flat surface disposed around an axis which crosses the surface and comprising elements of the preselected compound so that a first part of the surface of target member is positioned at a first sputtering position and another part of the first target member is positioned at a second sputtering position,at the first position, sputtering at least one second target comprising at least one element of the preselected compound which is easily sputtered from the first target member so as to supply the deficient element to the first target member, andat the second position, sputtering the elements from the first target member so as to deposit them on the surface of said substrate while continuously supplying the substrate so that a part of the substrate is positioned in the path of the sputtered elements,whereby the elementary composition of the first target member at the second position is adjusted to the preselected composition.