We present the third MAXI/GSC catalog in the high Galactic-latitude sky (|b| > 10 • ) based on the 7complementary to that in the low Galactic-latitude sky (|b| < 10 • ; Hori et al. 2018). We compile 682 sources detected at significances of s D,4−10 keV ≥ 6.5 in the 4-10 keV band. A two-dimensional image fit based on the Poisson likelihood algorithm (Cstatistics) is adopted for the detections and constraints on their fluxes and positions. The 4-10 keV sensitivity reaches ≈ 0.48 mCrab, or ≈ 5.9 × 10 −12 erg cm −2 s −1 , over the half of the survey area. Compared with the 37-month catalog (Hiroi et al. 2013), which adopted a threshold of s D,4−10 keV ≥ 7, the source number increases by a factor of ∼1.4. The fluxes in the 3-4 keV and 10-20 keV bands are further estimated, and hardness ratios (HRs) are calculated using the 3-4 keV, 4-10 keV, 3-10 keV, and 10-20 keV band fluxes. We also make the 4-10 keV lightcurves in one year bins for all the sources and characterize their variabilities with an index based on a likelihood function and the excess variance. Possible counterparts are found from five major X-ray survey catalogs by Swift , Uhuru, RXTE , XMM-Newton, and ROSAT , and an X-ray galaxy-cluster catalog (MCXC). Our catalog provides the fluxes, positions, detection significances, HRs, one-year bin lightcurves, variability indices, and counterpart candidates.