Disclosed are a beam combining/splitting modulator, a display apparatus including the same, and a spatial light modulation method. The beam combining/splitting modulator includes a light modulator including first and second modulation regions for modulating light, a polarization converter disposed at a side of an emitting surface of the light modulator and including a first transmissive region for polarizing and converting light incident from the first modulation region to have a first polarization and a second transmissive region for polarizing and converting light incident from the second modulation region to have a second polarization, a birefringence modulator disposed at the side of an emitting surface of the polarization converter and switching between a first state in which birefringence occurs and a second state in which birefringence does not occur, and a polarizer disposed at the side of an emitting surface of the birefringence modulator.