To provide a method for manufacturing a plain foil with a projecting foil as a constituent member of a metal honeycomb form on which a catalyst for cleaning an exhaust gas is deposited.

An array of projecting parts consisting of a desired number of projecting parts spaced at a desired interval is formed in the width direction of a long plain foil 1 at a first station S1 comprising a pair of upper and lower rolls A1, A11 for forming an array of projecting strips. In addition, a second-an n-station forming a desired number of arrays of projecting parts at a desired interval in the longitudinal direction of the plain foil. Further, when a step is completed at the n-station, each of the projecting parts forming the array of projecting parts forms a large number of projecting strips 1b installed parallel with the longitudinal direction of the plain foil and mutually connected to each other.