POWER OF ATTORNEY

The undersigned, as a Section 16 reporting person of
Komag Incorporated (the "Company"), hereby constitutes and appoints Jan
Schwartz and Kathleen A. Bayless, and each of them, the undersigned's true
and lawful attorney-in-fact to:

1.	complete and execute Forms 3, 4 and
5 and other forms and all amendments thereto as such attorney-in-fact shall
in his or her discretion determine to be required or advisable pursuant to
Section 16 of the Securities Exchange Act of 1934 (as amended) and the
rules and regulations promulgated thereunder, or any successor laws and
regulations, as a consequence of the undersigned's ownership, acquisition
or disposition of securities of the Company; and

2. do all acts
necessary in order to file such forms with the Securities and Exchange
Commission, any securities exchange or national association, the Company
and such other person or agency as the attorney-in-fact shall deem
appropriate.

The undersigned hereby ratifies and confirms all that said
attorneys-in-fact and agents shall do or cause to be done by virtue hereof.
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 (as amended).

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 Company and the foregoing
attorneys-in-fact.

	IN WITNESS WHEREOF, the undersigned has caused this
Power of Attorney to be executed as of this 20th day of May,
2003.


Signature: 	/s/ William Hammack

Print Name: 	William
Hammack