A neutral position locking apparatus that restricts a movement in a rack axis direction, of a rack shaft that steers rear wheels (2L, 2R), the neutral position locking apparatus comprising: a restriction pin having a first pin-sidewall portion (33, 133) that restricts the movement of the rack shaft in the rack axis direction at a neutral position, and a second pin-sidewall portion that restricts the movement of the rack shaft in the rack axis direction at a restriction position in which the rack shaft is offset from the neutral position in the rack axis direction; a pin-receiving portion formed in the rack shaft and having a first shaft-sidewall portion (41, 141) that is curved or slanted with respect to the pin axis and that restricts the movement of the rack shaft in the rack axis direction by making contact with the first pin-sidewall portion (33, 133) when the rack shaft is located at the neutral position, and a second shaft-sidewall portion that restricts the movement of the rack shaft by making contact with the second pin-sidewall portion when the rack shaft is located at the restriction position; and a driving device that moves the restriction pin in a projection direction in which the restriction pin moves toward the pin-receiving portion and in a removal direction in which the restriction pin moves away from the pin-receiving portion, wherein: the restriction pin and the pin-receiving portion are configured such that a contact force in the removal direction, which the second pin-sidewall portion receives from the second shaft-sidewall portion, is zero, or configured such that a contact force in the removal direction, which the second pin-sidewall portion receives from the second shaft-sidewall portion, is smaller than a contact force in the removal direction, which the first pin-sidewall portion (33, 133) receives from the first shaft-sidewall portion (41, 141). a restriction pin having a first pin-sidewall portion (33, 133) that restricts the movement of the rack shaft in the rack axis direction at a neutral position, and a second pin-sidewall portion that restricts the movement of the rack shaft in the rack axis direction at a restriction position in which the rack shaft is offset from the neutral position in the rack axis direction; a pin-receiving portion formed in the rack shaft and having a first shaft-sidewall portion (41, 141) that is curved or slanted with respect to the pin axis and that restricts the movement of the rack shaft in the rack axis direction by making contact with the first pin-sidewall portion (33, 133) when the rack shaft is located at the neutral position, and a second shaft-sidewall portion that restricts the movement of the rack shaft by making contact with the second pin-sidewall portion when the rack shaft is located at the restriction position; and a driving device that moves the restriction pin in a projection direction in which the restriction pin moves toward the pin-receiving portion and in a removal direction in which the restriction pin moves away from the pin-receiving portion, wherein: the restriction pin and the pin-receiving portion are configured such that a contact force in the removal direction, which the second pin-sidewall portion receives from the second shaft-sidewall portion, is zero, or configured such that a contact force in the removal direction, which the second pin-sidewall portion receives from the second shaft-sidewall portion, is smaller than a contact force in the removal direction, which the first pin-sidewall portion (33, 133) receives from the first shaft-sidewall portion (41, 141). the restriction pin and the pin-receiving portion are configured such that a contact force in the removal direction, which the second pin-sidewall portion receives from the second shaft-sidewall portion, is zero, or configured such that a contact force in the removal direction, which the second pin-sidewall portion receives from the second shaft-sidewall portion, is smaller than a contact force in the removal direction, which the first pin-sidewall portion (33, 133) receives from the first shaft-sidewall portion (41, 141).