A vehicle steering system that hardly gives a driver a feeling of strangeness even in mode switching is provided. Even if condition such as a defect of a system, which caused switching from SBW mode to EPS mode, has been resolved, a mode switching section waits for a timing of switching from EPS mode to SBW mode until a second condition is satisfied. The second condition is that the vehicle is in a certain state in which the driver hardly notices mode switching. The mode switching section waits for and judges a timing when the vehicle becomes into a certain state in which the driver hardly notices mode switching, and then performs switching from EPS mode to SBW mode.