A lamp having a planar light-emitting source includes a light-guiding structure, a light-emitting portion, and a shading supporting seat. The point-shaped lighting units of the light-emitting portion emit the point-shaped light beams toward the side plane of the light-guiding structure. Then, these beams enter the light-guiding structure. After turning approximately 90 degrees, a uniformly distributed planar light generated from the light-emitting plane of the light-guiding structure. So, a planar light source is obtained. In this invention, it has a planar light-emitting function with better lighting efficiency. The planar lighting is evenly distributed without shadow. Its energy consumption and heat generation are low. The product's life is prolonged. Its volume is small and it is portable.