An image sensor module includes an elongated light emitting unit, a photodetector, a lens unit, a substrate with the photodetector mounted on. The substrate is spaced apart from the lens unit in a thickness direction of the substrate. The image sensor module further includes a resin case provided with a light emitting unit chamber, a lens unit chamber and a substrate chamber. The lens unit chamber has a first bottom face extending in the first direction, and the substrate chamber has a second bottom face extending in the first direction and facing opposite to the first bottom face in the thickness direction of the substrate. The first or second bottom face is formed with at least one protrusion extending in the thickness direction of the substrate.