POWER OF ATTORNEY

	Know all by these presents, that the undersigned
hereby constitutes and appoints each of Jerome M. Schwartz, John K.
Lawrence, Verne C. Hampton, II, and Stephanie A. Asheim, signing singly,
the undersigned's true and lawful attorney-in-fact to:

(1)	execute for
and on behalf of the undersigned, in the undersigned's capacity as an
officer and/or director of Mercantile Bank Corporation (the "Company"),
Forms 3, 4, and 5 in accordance with Section 16(a) of the Securities
Exchange Act of 1934 and the rules thereunder; and Form ID, adopted by the
Securities and Exchange Commission.

(2)	do and perform any and all
acts for and on behalf of the undersigned which may be necessary or
desirable to complete and execute any such Form 3, 4, or 5, or Form ID, and
timely file such form with the United States Securities and Exchange
Commission and any stock exchange, stock market or similar authority; and


(3)	take any other action of any type whatsoever in connection with
the foregoing which, in the opinion of such attorney-in-fact, may be of
benefit to, in the best interest of, or legally required by, the
undersigned, it being understood that the documents executed by such
attorney-in-fact on behalf of the undersigned pursuant to this Power of
Attorney shall be in such form and shall contain such terms and conditions
as such attorney-in-fact may approve in such attorney-in-fact's discretion.


	The undersigned hereby grants to each such attorney-in-fact full
power and authority to do and perform any and every act and thing
whatsoever requisite, necessary, or proper to be done in the exercise of
any of the rights and powers herein granted, as fully to all intents and
purposes as the undersigned might or could do if personally present, with
full power of substitution or revocation, hereby ratifying and confirming
all that such attorney-in-fact, or such attorney-in-fact's substitute or
substitutes, shall lawfully do or cause to be done by virtue of this power
of attorney and the rights and powers herein granted.  The undersigned
acknowledges that the foregoing attorneys-in-fact, in serving in such
capacity at the request of the undersigned, are not assuming, nor is the
Company assuming, any of the undersigned's responsibilities to comply with
Section 16 of the Securities Exchange Act of 1934.

	This Power of
Attorney shall remain in full force and effect until the undersigned is no
longer required to file Forms 3, 4, and 5 with respect to the undersigned's
holdings of and transactions in securities issued by the Company, unless
earlier revoked by the undersigned in a signed writing delivered to the
foregoing attorneys-in-fact.

	IN WITNESS WHEREOF, the undersigned has
caused this Power of Attorney to be executed as of this 18th  day of July,
2005


														    /s/ John R. Zimmerman
				John R.
Zimmerman