This tractor is provided with: a hydraulic vertically driving unit 17 for vertically driving a towed tiller； and a mechanical coordination unit 18 for automatic vertical motion the mechanical coordination unit 18 converting the amount of change in a towed load into a vertical operation amount and transmitting the vertical operation amount to the vertically driving unit 17. The mechanical coordination unit 18 is provided with: a change amount conversion mechanism 33 having a load detection member 36 which rocks forward and backward in response to a towed load； and a link mechanism 34 for connecting in a coordinated manner the change amount conversion mechanism 33 and the vertically driving unit 17. The change amount conversion mechanism 33 has a rocking member 38 supported in a rockable manner by the load detection member 36 and connected in an coordinated manner to the vertically driving unit 17 through the link mechanism 34 and the change amount conversion mechanism 33 is configured so as to amplify by means of the relative rocking between the load detection member 36 and the rocking member 38 the amount of change in a towed load which is obtained by the forward and backward rocking of the load detection member 36 and then convert the amplified amount into the vertical operation amount.
