While light carrying orbital angular momentum (OAM) has much potential in increasing the bandwidth of communication networks, sorting of different OAM states is one of the key techniques to utilize it effectively. A method is proposed to realize optical coordinate transformation between two Fourier planes with the aid of spatial light modulator. After the transformations, the phase of light depending on azimuthal angle is changed to depend on transverse position. Each OAM state is focused to a lateral position after a phasecorrecting element. This method realizes sorting of light with OAM efficiently.