To provide a lateral light emitting device that can prevent coupling efficiency in a fused portion of a rod lens and a prism from being deteriorated, can set an outside diameter extremely small, and set the distance to a beam waist long. A lateral light emitting device includes an optical fiber 2, a rod lens 3, one end of which is fused to the end surface of the optical fiber 3, and a prism 4 fused to the other end of the rod lens. The prism has a base shape obtained by cutting a part of the circumference of a cylinder and forming a flat emission surface 4c parallel to an axial line. In a fused portion of the rod lens and the prism, the outside diameter of a fused end surface of the rod lens is equal to or smaller than the smallest diameter of a fused end surface of the prism. The fused end surface of the rod lens does not protrude from the fused end surface of the prism. A center O1 of the fused end surface of the rod lens and a center O2 of a circular arc of the fused end surface of the prism are offset.