To provide a riding type moving agricultural machine easy in adjusting a tread.

A front wheel and a rear wheel 3 are suspendedly mounted in a lower part of a wheel shaft support member 74 from a front axle case and a rear axle case 70 integrally mounted in a machine body, and the wheel shaft support member 74 is formed so that its length Y is longer than a radius X of the front wheel or the rear wheel 3. Thus, the front wheel and the rear wheel 3 are replaceably constituted on the inside and the outside of the machine body by sandwiching a kingpin shaft 75. A worker inserts a wheel shaft 83 into a wheel shaft transmission cylinder 81 from the inside of the machine body, and fixes by a locking pin 63, in the case of a wide ridge A, and inserts the wheel shaft 83 into the wheel shaft transmission cylinder 81 from the outside of the machine body, and fixed by the locking pin 63, when straddling two narrow ridges B, and the treads ST are adjusted in response to the ridge size.