PROBLEM TO BE SOLVED: To simplify a wheel support structure of a rice planter and reduce its weight by incorporating a differential mechanism in a cylindrical axle case, forming a connection part for a wheel case at both ends of the case, and provid ing a drive linkage mechanism which operates a differential lock mechanism in the vicinity of the connection part on one side. SOLUTION: An annular groove type engaging part 51B is provided in an end part on the opposite side from a claw type engaging part 51A of a differential lock case 51 and is extended close to a flange part 11A which becomes a connection part to a front wheel case 53 of a front axle case 11 to constitute a differential lock mechanism R by a differential case 46 and the claw type engaging part 51A. A support boss 11B is erected in the vicinity of the flange part 11A, a rotary shaft is fitted in the support boss 11B, and a clutch yoke 55 is fixed in an inner end which enters the front axle case 11 of a rotary shaft and is engaged with the engaging part 51B. A relay support point 56 is provided in an outer end part of the support boss 11B and is linked to a differential lock operation tool to constitute a drive linkage mechanism which operates the differential lock mechanism R. Consequently, it is possible to simplify a wheel support structure of a rice planter and reduce its weight.
