One of the mode lamps 38a, 38b and 38c of the mode indicator 38 corresponding to the current steering mode is turned on yellow and the other mode lamps are turned on green or turned off, thereby indicating whether front wheels 1, 1 and rear wheels 2, 2 are at neutral. A controller 39 does not operate a mode changing valve 24 even with an instruction outputted from a mode change switch 35 when the front and rear wheels are not at neutral, and operates, in response to an instruction outputted from the mode change switch 35, the mode changing valve 24 to establish a steering mode corresponding to the instruction when the front and rear wheels are at neutral. Also, the mode indicator 38 is controlled to always indicate, as the current steering mode, one corresponding to the steering mode actually established by the mode changing valve 24. With those features, in a working vehicle in which the mode of steering front and rear wheels can be changed over between two-wheel steering and four-wheel steering, a steering system having superior operability and high reliability can be provided.