WEST is a package for calculating excited spectrum by using the one-shot GW method. Before calculating the excited spectrum, it is necessary to obtain the ground states from the DFT calculations (LDA/GGA/hybrid functional) by Quantum ESPRESSO. To reduce the numerical cost, WEST uses the algorithm that does not require the unoccupied bands. It is also possible to include the spin-orbit couplings and to perform the large-scale calculations at supercomputers. Installation and formats of input files are basically the same as those of Quantum ESPRESSO.