The present disclosure relates to a collimator for radiation generating apparatus, attached to a radiation generating apparatus, the collimator comprising: a frame fixed to the radiation generating apparatus and formed in a ring shape; and a shielding adjustment part provided with a plurality of shielding wings, one end of the shielding wings being hinged to the frame such that, when rotated, the other end of the shielding wings enters into a center of the frame, and the each one end of the shielding wings being disposed to be spaced apart on the frame, wherein the shielding wing is made of a radiation shielding metal. Accordingly, it is possible to easily adjust the diameter of radiation field made in a circular shape.