An orthogonal complex spreading method for a multichannel and an apparatus thereof are disclosed. The method includes the steps of complex-summing .alpha..sub.n1W.sub.M,n1X.sub.n1 which is obtained by multiplying an orthogonal Hadamard sequence W.sub.M,n1 by a first data X.sub.n1 of a n-th block and .alpha..sub.n2W.sub.M,n2X.sub.n2 which is obtained by multiplying an orthogonal Hadamard sequence W.sub.1,n2 by a second data X.sub.n2 of a n-th block; complex-multiplying .alpha..sub.n1W.sub.M,n1X.sub.n1+j.alpha..sub.n2W.sub.M,n2X.sub.n2 which is summed in the complex type and W.sub.M,n3+jPW.sub.M,n4 of the complex type using a complex multiplier and outputting as an in-phase information and quadrature phase information; and summing only in-phase information outputted from a plurality of blocks and only quadrature phase information outputted therefrom and spreading the same using a spreading code.