To provide a light source device for document reading where a subordinate board mounted on a main board is free of failures, such as disconnections due to breaking of lead parts in a light source device which has an inverter circuit board for lighting a lamp mounted on a light source part.

The light source device for document reading, which reads a document by irradiating a document surface with a light and receiving the light reflected from the document surface, has a light source and a light source lighting device integrated and movable in a document reading direction, when the document is read, and the light source lighting device has an electronic component mounted on the main board, that the subordinate board erected on the main board, and a free end of a large-sized component on the subordinate board is glued and fixed to the main board with silicon adhesives.