Single photon emission computed tomography system for the measurement of the distribution of externally administered radionuclides in human body has been developed and its performance is studied. GAMMATOM-II consists of 36 NaI(T$\ell$) scintillation detectors of 2 cm (dia.)$\times$3.8 cm (length). The detectors are arranged into four separate banks each of which consists of nine detectors. Each detector bank is arranged in a circular arc shape and is displaced 1/4 detector width each other from center. Using collimators which have converging multiple holes and new sampling scheme, spatial resolution of 7 mm FWHM was obtained with 15 cm diameter resolution phantom. Sensitivity of the system was observed as counts of 100 (counts/sec)/($\mu$Ci/cc) with 28 cm diameter uniform disk phantom filled with $^{99m}$Tc.