To provide a housing fixing structure and a housing fixing method capable of preventing fixing failure of a fastening part caused by fastening-fixation without thickening the thickness of the fastening part, when fastening and fixing a housing to a fixing structure by inserting a fixing member into the fastening part.

When fastening and fixing a rein housing 2 forming the fastening part 17 having an insertion hole 18 to the fixing structure by inserting the fixing member into the insertion hole 18 of the fastening part 17, a plurality of projection parts 25 biting in the fixing structure are formed in the fastening part 17. When the projection parts 25 bite in the fixing structure, counteracting force of the rotational moment acting on the fastening part 17 is generated, and the fixing failure of the fastening part 17 is prevented.