A light-emitting device for a motor vehicle, including a housing and a light source assembly arranged in the housing, wherein the light-emitting device further includes a substantially plate-shaped light guide including an opening portion, and the light guide is positioned in such a way that the light source assembly is located behind the opening portion in a main emitting direction of the light-emitting device or located in the center of the opening portion, thereby transmitting lateral light from the light source assembly into the light guide. According to the light-emitting device of the present invention, the light rays from the light source assembly are expanded through the light guide, and can be used to display a decorative pattern, thereby providing more lighting decorative design styles and improving the aesthetic appearance.