January 25, 2018

BlackRock Municipal Bond Fund, Inc.

100 Bellevue Parkway

Wilmington, Delaware 19809

Ladies and Gentlemen:

We have acted as special Maryland counsel to BlackRock Municipal Bond Fund, Inc., a Maryland corporation (the “Company”), in connection with the registration under the Securities Act of 1933, as amended (the “Act”), of 2,000,000,000 shares of the Company’s common stock, par value $0.10 per share, designated as Class K Shares (the “Class K Stock”), on its Registration Statement on Form N-1A filed with the Securities and Exchange Commission on the date hereof (File No. 002-57354, together with all amendments and supplements thereto but exclusive of the exhibits thereto, the “Registration Statement”).

We have examined the Registration Statement and such corporate records, certificates and documents as we deemed necessary for the purpose of this opinion. We have relied as to certain factual matters on information obtained from public officials and officers of the Company. Based on that examination, we advise you that in our opinion the shares of the Class K Stock offered by the Company have been duly authorized and, assuming that upon any issuance of Class K Stock the total number of shares of Class K Stock issued and outstanding will not exceed the total number of shares of Class K Stock that the Company is then authorized to issue under its charter, when issued under the circumstances contemplated in the Registration Statement against payment therefor, will be legally issued, fully paid and non-assessable.

We express no opinion with respect to the laws of, or the effect or applicability of the laws of, any jurisdiction other than, and our opinion expressed herein is limited to, the laws of the State of Maryland. The opinion expressed herein is limited to the matters expressly set forth in this letter and no other opinion should be inferred beyond the matters expressly stated.

We hereby consent to the filing of this opinion as an exhibit to the Registration Statement. In giving our consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Securities and Exchange Commission thereunder.

Very truly yours,
Miles & Stockbridge P.C.
By:	/s/ Christopher R. Johnson
	Principal