Exhibit 5.1

[Dorsey & Whitney LLP Letterhead]

October 18, 2002

Apogee Enterprises, Inc.

7900 Xerxes Avenue South, Suite 1800

Minneapolis, Minnesota 55431

Re:    Registration Statement on Form S-8

Ladies and Gentlemen:

Reference is made to the Registration Statement on Form S-8 (the “Registration Statement”) that you intend to file with the Securities and Exchange Commission pursuant to the Securities Act of 1933, as amended, for the purpose of registering up to 1,800,000 shares (the “Shares”) of common stock, par value $.33 1/3 per share, of Apogee Enterprises, Inc., a Minnesota corporation (the “Company”). The Shares will be issuable under the Apogee Enterprises, Inc. 2002 Omnibus Stock Incentive Plan (the “Plan”).

We have examined such documents and have reviewed such questions of law as we have considered necessary and appropriate for the purposes of our opinions set forth below.

In rendering our opinions set forth below, we have assumed the authenticity of all documents submitted to us as originals, the genuineness of all signatures and the conformity to authentic originals of all documents submitted to us as copies. As to questions of fact material to our opinions, we have relied upon certificates and representations of officers of the Company and of public officials.

Based on the foregoing, we are of the opinion that the Shares have been duly authorized and, upon issuance, delivery and payment therefor in accordance with the terms of the Plan, will be validly issued, fully paid and nonassessable.

Our opinions expressed above are limited to the laws of the State of Minnesota.

We hereby consent to the filing of this opinion as an exhibit to the Registration Statement.

Very truly yours,

/s/    Dorsey & Whitney LLP

RAR