A two-side illuminating lens body mainly projecting light from a light emitting device to two relative outer directions includes a base with a receiving slot having a downwards opening for receiving a lighting device. A concave arc for receiving the light emitting portion of the lighting device is formed above the receiving slot as a light incident side. On a top surface of the base, two symmetrical non-spherical protrusions are jointly arranged beside a center light axis. A concave curved surface is formed to a border of the two non-spherical protrusions. Two symmetrical awl laterals are formed on relative outer edges of the non-spherical protrusions. Through three different refracting types of the concave curved surface, non-spherical protrusions, and awl laterals, rays from the light emitting device will be gradually diffused away from the center light axis so that a double-side skew light distribution of illumination like a butterfly is projected.