A lamp module mounted on a housing is provided. The lamp module includes a lamp and a lamp sleeve. The plane perpendicular to an optical of the lamp has an x-axis direction and a y-axis direction mutually perpendicular to each other. The lamp is mounted within the lamp sleeve, and a positioning piece is formed at one end of the lamp sleeve for mounting the lamp sleeve on the housing. The positioning piece at least includes a first surface and a second surface respectively parallel to the x-axis direction and the y-axis direction. At least one of the first surface and the second surface is equipped with an adjustable apparatus for adjusting the alignment of the lamp by moving the positioning piece along the direction(s) of the x-axis or/and the y-axis. The adjustable apparatus comprises a positioning component, a fastener and an elastic component.