The present invention provides a tractor which can prevent leaking of oil. In a tractor which forms a transmission casing by communicably connecting a plurality of cylindrical casings in the fore-and-aft direction, a shaft-support-wall forming body is detachably mounted on an inner peripheral portion of an end portion of one cylindrical casing, and end surfaces of the cylindrical casing are brought into face contact with each other and are connected with each other without interposing the shaft-support-wall forming body therebetween.