The existence of lensed quasars with splitting angles larger than $7''$ has been predicted on the basis of the cold dark matter model. We searched for these large-separation lensed quasars from the spectroscopically classified $\sim40,000$ quasars obtained by the Sloan Digital Sky Survey (SDSS), and succeeded in discovering the first lensed quasar by a cluster of galaxies, SDSS J1004+4112: It consists of four images, and the maximum separation is $14.62''$. Here we describe the discovery and the follow-up observations of this system, as well as the latest results of the large-separation lens search in the SDSS. We also present the new statistical model which fully incorporates non-sphericity of dark halos, and compare the theoretical predictions with the SDSS results.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html