Exhibit 32(b)

                Certification Pursuant to 18 U.S.C. Section 1350

      I, Mark J. Plush, Vice President and Chief Financial Officer of Keithley
Instruments, Inc. (the "Company"), certify, pursuant to 18 U.S.C. Section 1350,
that:

      (1) The Quarterly Report on Form 10-Q of the Company for the period ended
      March 31, 2004 which this certification accompanies fully complies with
      the requirements of section 13(a) or 15(d) of the Securities Exchange Act
      of 1934; and

      (2) The information contained in the Report fairly presents, in all
      material respects, the financial condition and results of operations of
      the Company.



/s/ Mark J. Plush
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Mark J. Plush
Vice President and Chief Financial Officer
May 14, 2004


A signed original of this written statement has been provided to Keithley
Instruments, Inc. and will be retained by Keithley Instruments, Inc. and
furnished to the Securities and Exchange Commission or its staff upon request.