We have observed a 0.7×1.2deg2 field in the SGP region with the UT / NAOJ Mosaic CCD Camera attached to the 40-inch Swope Telescope at Las Campanas Observatory, and constructed a sample of 1150 galaxies in the region down to R=20.5. Then we applied to the sample a new, objective cluster-finding technique, which is an improved variant of the so-called “matched-filter technique” pioneered by Postman et al. (1996). Using projected positions and apparent magnitudes of galaxies simultaneously, this technique can, not only find cluster candidates, but also estimate their redshifts and richnesses. A number of Monte Carlo simulations demonstrated enough accuracies of the estimations and much lower spurious detection rate than that by conventional cluster-finding methods which use only surface density of galaxies.