We report the observation on the magnetic property of the stable Zn77Fe7Sc16 icosahedral quasicrystal discovered recently. As a result of measurements of magnetization, it became clear that the new Zn-based icosahedral quasicrystal has large local magnetic moments and exhibits spin glass behavior. The magnetization curves show Curie-like paramagnetism, where the magnetization M is 4.45 cgsemu/g at 5 K under 70 kOe. The temperature dependence, of the magnetic susceptibility obeys the Curie-Weiss law between 76 and 300 K. On the assumption that all of the Fe atoms have the same magnitude of local magnetic moment, the effective number of Bohr magneton p of each Fe atom was estimated at 5.30 on average. Moreover, in the low-temperature region, the spin glasslike cusp of the magnetic susceptibility was observed with a freezing temperature T-f = 7.2 K.