An optical module of an optical mouse includes a light source, a light-guiding unit having a fixing portion, a first lens and a second lens. A housing of the light source includes a substantially plane light-emitting surface, and the light-guiding unit guides light emitted by the light source. The fixing portion is disposed on one side of the light-guiding unit for fastening the light source. The first lens is disposed on one side of the fixing portion close to the light-guiding unit for focusing the light emitted by the light source onto a working surface. The second lens is disposed on an optical path between the light source and the first lens using injection molding for focusing the light provided by the light source onto a focal point of the first lens.