A lens fixing structure for an optical module of a scanner, a multi-function printer, a fax machine or a copy machine is disclosed. The lens fixing structure for an optical module of a scanner, a multi-function printer, a fax machine or a copy machine, wherein the optical module has a housing, and the lens fixing structure is installed on the housing, includes a slot structure for placing and fixing a lens therein, wherein the slot structure includes a first slot wall positioned on the housing; and a second slot wall positioned on the housing and being parallel to the first slot wall, wherein the second slot wall is perpendicular to a surface of the housing.