An apparatus that adaptively allocates transmission power for beam-forming combined with orthogonal space time block codes in a distributed wireless communication system, the apparatus including: sub-arrays for beam-forming, which are geographically distributed and each of which includes a plurality of distributed antennas placed in random groups. A central processing unit provides predetermined combinable power allocation schemes according to subsets in a plurality of the sub-arrays, identifying performances of the schemes by using information on large-scale fading of each of the sub-arrays fed back from a receiving party, setting a subset having best performance as an optimal subset according to the identified performances, and performing power allocation according thereto.