Heavy fermion behaviors observed in the amorphous(a-) Ce_9Cu_ alloy are markedly suppressed by applying high magnetic fields, H. The electronic specific heat coefficient, which is extremely large at H=0 Oe becomes smaller for H>100 kOe. With increasing H, the magnetization curve increases nonlinearly, where the magnetic susceptibility estimated for H>100 kOe is one order smaller than that for H<10 kOe. At 4.2 K, the magnetoresistance is negative and its absolute value is very small owing to the disorder scattering. These features indicate that a dense Kondo behavior is strongly suppressed in a high magnetic field
