Provided is a steering system for construction, transportation, and agricultural machines that can be steered using a steering wheel and lever (or automatic steering) in which a mechanism for prioritizing steering wheel operation can be realized that has a simple configuration and that always operates stably, the steering system comprising steering cylinders 1, a steering valve 2, a pump 3, a steering wheel control valve 4, an electromagnetic control valve 5 for the lever or automatic steering, a steering wheel prioritizing valve 6, and a switching valve 7, for sensing the load pressure generated when the steering wheel control valve 4 is operated and switching the steering wheel prioritizing valve 6 using the load pressure, wherein the switching valve 7 for switching the steering wheel prioritizing valve 6 has a two-port, two-position configuration in which the fluid draining passage of the steering wheel prioritizing valve 6 is closed using the load pressure generated when the steering wheel control valve 4
