A rack shaft support device includes: a rack shaft support member that slidably supports a rack shaft; a sealing member fixed to an inlet port of a retention hole formed in a housing; an intermediate member that is interposed between the rack shaft support member and the sealing member; a torsion spring that couples the intermediate member so that torque is transmitted to the intermediate member; a torsion amount adjusting member that is attached to the sealing member in such a manner that a position of the torsion amount adjusting member with respect to the sealing member is adjustable and adjusts a torsion amount of the torsion spring; and a cam mechanism that converts a rotation force of the intermediate member induced by untwisting of the torsion spring into a force by which the intermediate member pushes the rack shaft support member.