The invention discloses a lens device and a lamp adopting the above lens device. The lens device comprises a conical lens body, wherein a hemispherical notch is formed in the lower part of the conical lens body; the central shaft of the hemispherical notch and that of the conical lens body coincide; a plurality of spherical-segment light incidence grooves are uniformly formed in the conical lens body in the hemispherical notch; a conical notch is formed in the upper end surface of the conical lens body; and the bottom surface of the conical notch and the upper bottom surface of the conical lens body coincide. In order to overcome defects in the prior art, the lens device is provided. Furthermore, the lamp adopting the above lens device as well as being good in heat-dissipating effect and long in service life is provided.