EXHIBIT 5.1

                          PILLSBURY MADISON & SUTRO LLP
                                50 Fremont Street
                             San Francisco, CA 94105
                               Tel: (415) 983-1000


                                February 7, 2000




SJNB Financial Corp.
One North Market Street
San Jose, California 95113


          Re: Registration Statement on Form S-8


Ladies and Gentlemen:

     We refer to the  Registration  Statement  on  Form S-8  (the  "Registration
Statement") to be filed by SJNB Financial  Corp., a California  corporation (the
"Registrant"),  with the Securities and Exchange Commission under the Securities
Act of 1933,  as  amended,  relating  to 184,082  shares of Common  Stock of the
Registrant  (the  "Shares")  issuable  upon the  exercise of options  originally
granted by Saratoga Bancorp ("Saratoga").  The Shares to be registered hereunder
are issuable by the  Registrant  pursuant to options  assumed by the  Registrant
pursuant to an Agreement and Plan of Merger,  dated as of August 27, 1999, among
the Registrant,  Saratoga and Saratoga National Bank. Such options relate to (i)
the Saratoga  Bancorp 1982 Stock Option Plan and (ii) the Saratoga  Bancorp 1994
Stock  Option  Plan (the  "Plans").  We advise you that,  in our  opinion,  such
Shares, when issued and sold in accordance with the Plans and, where applicable,
with option  agreements duly  authorized  under the Plans and in accordance with
the   Registration   Statement,   will  be  legally   issued,   fully  paid  and
nonassessable.

     We hereby  consent to the filing of this  opinion with the  Securities  and
Exchange Commission as Exhibit 5.1 to the Registration Statement.

     This opinion  letter is rendered as of the date first  written above and we
disclaim  any  obligation  to  advise  you of  facts,  circumstances,  events or
developments  which  hereafter  may be  brought to our  attention  and which may
alter,  affect or modify the opinion expressed herein.  Our opinion is expressly
limited to the  matters  set forth  above and we render no  opinion,  whether by
implication or otherwise,  as to any other matters  relating to the  Registrant,
the Plans or the Shares.

                                Very truly yours,


                                /s/ PILLSBURY MADISON & SUTRO LLP