An illuminator, a scanner module and an apparatus are provided. The scanner module includes an illuminator that includes a light source, a light guide extending in a main scanning direction to change a direction of the light from the light source, a guide holder recessed with a light guide mounting portion in which the light guide is mounted, and at least one supporting protrusion protruding from an entrance of the light guide mounting portion into the light guide mounting portion to support the light guide received in the light guide mounting portion. As the light guide is supported by the supporting protrusion formed at the entrance of the light guide mounting portion, it is possible to reduce deformation of the light guide and/or to prevent the light guide from being falling out of the light guide mounting portion when subjected to, e.g., a shock.