A blind spot warning indication device for an exterior mirror of an automobile includes a light guide member. A plurality of wedge-shaped bosses are arranged side by side along an axis on the light guide member corresponding to a setting direction of the PCB. One side of each of the plurality of wedge-shaped bosses has a light incident end surface for aligning with a corresponding light source. An upper surface of each of the plurality of wedge-shaped bosses includes a light reflecting side having an optical pattern for reflecting and scattering. The reflecting side having the optical pattern is an upwardly convex arc surface. A lower surface of the wedge-shaped boss has a light emitting side. The outermost wedge-shaped boss has the largest curvature of the light-reflecting side compared to the other wedge-shaped bosses arranged side by side, and the outermost wedge-shaped boss has the longest length of the light-emitting side compared to the other wedge-shaped bosses arranged side by side. The device has the functions of reflection and scattering at the same time. The uniformity of the emitted light at the front surface and certain angles is better, and the warning effectiveness is improved. The LOGO pattern can be better combined with the emitted light.