To constitute a step supporting structure so as to readily carry out attaching and detaching of a step part when the step part is attached to right and left parts of an operating part in a paddy field working vehicle.

Supporting pins 32d, 55a and 59a in the longitudinal direction of a machine body are provided in either one of a step part 50 and a fixed parts 32 and 60 on machine body side, and supporting holes 32e, 54a and 60a in longitudinal directions of the machine body are provided in the other thereof and contact parts 31 and 32f for preventing the step part 50 from swinging to the lower direction by contact with the step part 50 are provided on the machine body side. A preventing member 61 for preventing escape of supporting pins 32d, 55a and 59a from the supporting holes 32e, 54a and 60a is provided in the step-supporting structure.