A rack shaft supporting device comprising: a fixing member fixed to a housing; a support yoke that supports a rack shaft so that the rack shaft is slidable; a support member that is provided between the fixing member and the support yoke, and that supports the support yoke; an intermediate member provided between the fixing member and the support member; a cam mechanism including paired cam surfaces (22, 23) provided either in paired facing surfaces of the fixing member and the intermediate member or in paired facing surfaces of the intermediate member and the support member, the paired cam surfaces being engaging with each other; a rotational force applying spring that rotates members in which the paired cam surfaces are formed, relative to each other; a washer provided between a first surface constituted by either one of paired facing surfaces of the support member and the support yoke, and a second surface constituted by the other of the paired facing surfaces, the washer having an insertion hole formed therein; characterized by a compression spring provided between the second surface and the washer and pressing the support yoke toward the rack shaft; and a set length regulation mechanism that regulates a set length of the compression spring, wherein the set length regulation mechanism includes: a recessed portion provided in the first surface; a projection shaft including a proximal end portion fixed to the second surface and a distal end portion provided with a receiving portion that receives the washer, the projection shaft being inserted through the insertion hole of the washer so as to project into the recessed portion; and a positioning stepped portion provided in either one of the proximal end portion and the distal end portion of the projection shaft, the positioning stepped portion abutting on a corresponding one of the second surface and the receiving portion. a fixing member fixed to a housing; a support yoke that supports a rack shaft so that the rack shaft is slidable; a support member that is provided between the fixing member and the support yoke, and that supports the support yoke; an intermediate member provided between the fixing member and the support member; a cam mechanism including paired cam surfaces (22, 23) provided either in paired facing surfaces of the fixing member and the intermediate member or in paired facing surfaces of the intermediate member and the support member, the paired cam surfaces being engaging with each other; a rotational force applying spring that rotates members in which the paired cam surfaces are formed, relative to each other; a washer provided between a first surface constituted by either one of paired facing surfaces of the support member and the support yoke, and a second surface constituted by the other of the paired facing surfaces, the washer having an insertion hole formed therein; characterized by a compression spring provided between the second surface and the washer and pressing the support yoke toward the rack shaft; and a set length regulation mechanism that regulates a set length of the compression spring, wherein the set length regulation mechanism includes: a recessed portion provided in the first surface; a projection shaft including a proximal end portion fixed to the second surface and a distal end portion provided with a receiving portion that receives the washer, the projection shaft being inserted through the insertion hole of the washer so as to project into the recessed portion; and a positioning stepped portion provided in either one of the proximal end portion and the distal end portion of the projection shaft, the positioning stepped portion abutting on a corresponding one of the second surface and the receiving portion. a recessed portion provided in the first surface; a projection shaft including a proximal end portion fixed to the second surface and a distal end portion provided with a receiving portion that receives the washer, the projection shaft being inserted through the insertion hole of the washer so as to project into the recessed portion; and a positioning stepped portion provided in either one of the proximal end portion and the distal end portion of the projection shaft, the positioning stepped portion abutting on a corresponding one of the second surface and the receiving portion.