May 18, 1998

HSB Group, Inc.
One State Street
P.O. Box 5024
Hartford, CT  06102-5024

Ladies and Gentlemen:

In reference to the Registration  Statement of HSB Group, Inc.  (hereinafter the
"Company") on Form S-3 (the  "Registration  Statement") that is being filed with
the Securities and Exchange Commission in connection with the proposed offer and
sale by certain  shareholders of the Company (the "Selling  Shareholders") of up
to 205,174  shares (as adjusted for the  three-for-two  stock split  declared on
April 24, 1998 with a May 1, 1998 record  date and May 22,  1998  payable  date)
(the  "Shares") of the  Company's  Common  Stock  without par value (the "Common
Stock"),  you have asked my opinion as General  Counsel of the  Company,  on the
validity  of the  issuance  of the  Shares.  As  described  in the  Registration
Statement,  sales of the Shares by the Selling Shareholders may be effected from
time to time in one or more transactions,  including block trades, in negotiated
transactions or in a combination of such methods of sale.

In rendering this opinion,  I, or attorneys under my supervision,  have examined
the Company's  Articles of Incorporation and By-laws as presently in effect, and
such other records of the Company which I deem  necessary or  appropriate  under
the circumstances.

Based on the  foregoing,  I am of the opinion  that the Shares to be sold by the
Selling  Shareholders  have been duly authorized and are validly  issued,  fully
paid and nonassessable shares of Common Stock of the Company.

I hereby consent to the inclusion in said Registration Statement of this opinion
as an exhibit thereto.

Sincerely yours,

/s/ Robert C. Walker
Robert C. Walker
Senior Vice President and
General Counsel