Exhibit 23(b)



                        Consent of Independent Auditors


We consent to the reference to our firm under the caption "Experts" and to the
incorporation by reference herein of our report dated January 16, 2001, with
respect to the consolidated financial statements of National City Bancorporation
included in its Annual Report to Shareholders which is incorporated by reference
in its Annual Report on Form 10-K incorporated by reference in the Registration
Statement (Form S-4) and related Prospectus of Marshall & Ilsley Corporation for
the registration of 5,850,000 shares of its common stock.

/s/ Ernst & Young LLP

Minneapolis, Minnesota
May 30, 2001