A method for manufacturing a phase mask and a lens-less camera module comprises the steps of: obtaining a replica mold on which an inverted phase shift pattern is formed in which a phase shift pattern of a master phase mask spaced apart from an image sensor is inverted; calculating a thickness of a phase mask disposed on the image sensor replacing the master phase mask; arranging a photocurable material for implementing the phase mask on the image sensor to a calculated thickness, placing the replica mold on an upper surface of the photocurable material, and then curing the photocurable material; and removing the replica mold from the top of the phase mask, so that the focal distance change or parallel movement does not occur depending on the position of the phase mask.