If the density distribution \rho ( r ) of MACHOs is spherically symmetric with respect to the Galactic center , it is shown that the minimal total mass M _ { min } ^ { { MACHO } } of the MACHOs is 1.7 \times 10 ^ { 10 } M _ { \sun } \tau _ { -6.7 } ^ { { LMC } } where \tau _ { -6.7 } ^ { { LMC } } is the optical depth ( \tau ^ { { LMC } } ) toward the Large Magellanic Cloud ( LMC ) in the unit of 2 \times 10 ^ { -7 } .
If \rho ( r ) is a decreasing function of r , it is proved that M _ { min } ^ { { MACHO } } is 5.6 \times 10 ^ { 10 } M _ { \sun } \tau _ { -6.7 } ^ { { LMC } } .
Several spherical and axially symmetric halo models of the Galaxy with a few free parameters are also considered .
It is found that M _ { min } ^ { { MACHO } } ranges from 5.6 \times 10 ^ { 10 } M _ { \sun } \tau _ { -6.7 } ^ { { LMC } } to \sim 3 \times 10 ^ { 11 } M _ { \sun } \tau _ { -6.7 } ^ { { LMC } } .
For general case , the minimal column density \Sigma _ { min } ^ { { MACHO } } of MACHOs is obtained as \Sigma _ { min } ^ { { MACHO } } = 25 M _ { \sun } { pc } ^ { -2 } \tau _ { -6.7 } ^ { { LMC } } . If the clump of MACHOs exist only halfway between LMC and the sun , M _ { min } ^ { { MACHO } } is 1.5 \times 10 ^ { 9 } M _ { \sun } .
This shows that the total mass of MACHOs is smaller than 5 \times 10 ^ { 10 } M _ { \sun } , i.e . \sim 10 % of the mass of the halo inside LMC , either if the density distribution of MACHOs is unusual or \tau ^ { { LMC } } \ll 2 \times 10 ^ { -7 } .

( 11 October 1996 , Accepted for publication in Apj .
Letters . )