A rack bar supporting device is a device for supporting a rack bar of a steering apparatus of a vehicle toward a pinion shaft and includes a rack bearing and a biasing assembly. The biasing assembly includes an adjustment plug, an adjustment assembly and a support plate assembly. The adjustment assembly includes an adjustment member and a first biasing member. The support plate assembly includes a first support plate, a second support plate, a second biasing member which provides a force for pushing the first support plate along the biasing axis against the second support plate, and a connection structure which connects the first and the second support plates together so as to restrict movement of the second plate in a direction away from the rack bearing.