A method of heat-treating a rack bar includes a step of continuously conveying a rack bar provided with a rack teeth portion and a ball screw portion by a quenching means, and a step of sequentially applying a quenching treatment to each circumferential surface of the rack teeth portion and the ball screw portion. The quenching treatment is preferably and sequentially applied to each entire circumferential surface of the rack teeth portion and the ball screw portion.