Disclosed is an apparatus for protecting impact to a rack bar of a power steering gearbox comprising an oil pressure cylinder, to which oil which has passed through an oil pressure pump and a rotary valve is supplied through a left port or right port, a rack bar disposed in the oil pressure cylinder and horizontally reciprocating, a piston fixed at the middle of the rack bar, a first lack bush and a second lack bush disposed at both ends of the cylinder, in which the piston moves, to close the cylinder, and bypass holes with a downward convex shape disposed at both ends of the cylinder adjacent to the first and second rack bushes, in which a part of oil pressure is released immediately before a piston of the rack bar moving by the power of oil pressure reaches a rack bush, whereby impact to the cylinder or noise is not generated.