EXHIBIT 21

                               SEMCO ENERGY, INC.

                              List of Subsidiaries
                         Exhibit 21 to Form 10-K (2005)


As of December 31, 2005, the subsidiaries of SEMCO Energy, Inc. (the Registrant)
were:

- -     Alaska Pipeline Company, an Alaska corporation
- -     NORSTAR Pipeline Company, Inc., an Alaska corporation (a subsidiary of
      Alaska Pipeline Company)
- -     Hotflame Gas, Inc., a Michigan corporation
- -     SEMCO Construction Parent Company (formerly known as EnStructure
      Corporation, Sub-Surface Resources, Inc. and prior thereto, NATCOMM,
      Inc.), a Michigan corporation
- -     SEMCO Energy Ventures, Inc., a Michigan corporation
- -     SEMCO Gas Storage Company, a Michigan corporation (a subsidiary of SEMCO
      Energy Ventures, Inc.)
- -     SEMCO Pipeline Company, a Michigan corporation (a subsidiary of SEMCO
      Energy Ventures, Inc.)
- -     SEMCO Information Technology, Inc. (formerly known as Aretech Information
      Services, Inc.), a Michigan corporation

Each of the above-listed companies does business only under its respective
corporate name as indicated above, except as follows:

- -     SEMCO Energy, Inc. does business in Alaska under the name ENSTAR Natural
      Gas Company and in Michigan as Battle Creek Gas Company, Peninsular Gas
      Company and SEMCO Energy Gas Company.