To smoothly collect lawn grass by constituting a large duct in a tractor for a mower in which a mower is arranged between the front wheels and the rear wheels of a vehicle body and lawn grass reaped by the mower is collected through the dust installed between the right and left rear wheels in a lawn grass storage case at the rear part of the vehicle body.

This tractor for the mower has constitution that the mower 52 is arranged between the front wheels 8 8 and the rear wheels 34 and 45 of the vehicle body and lawn grass reaped by the mower 52 is collected through the duct 61 installed between the right and left rear wheels 34 and 45 in the lawn grass storage case 57 at the rear part of the vehicle body. Power changed in speed by a speed change means arranged above the duct 61 is transmitted to the power transmission means of a rear wheel transmission case 23 and a differential mechanism 35 installed at the right side of the duct 61, and then the power transmitted to the differential mechanism 35 is transmitted through right and left running transmission shafts 39 and 36 installed below the duct 61 to the right and left rear wheels 45 and 34.