An orthogonal complex spreading method for a multichannel and an apparatus thereof are disclosed. The method includes the steps of complex-summing &agr;n1WM,n1Xn1 which is obtained by multiplying an orthogonal Hadamard sequence WM,n1 by a first data Xn1 of a n-th block and &agr;n2WM,n2Xn2 which is obtained by multiplying an orthogonal Hadamard sequence W1,n2 by a second data Xn2 of a n-th block; complex-multiplying &agr;n1WM,n1Xn1+j&agr;n2WM,n2Xn2 which is summed in the complex type and WM,n3+jPWM,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.