This study aims to reveal the economic conditions of corn contractors who use large self-propelled har vesters; we do so by examining the corn double-cropping area in warm southwestern districts in Japan. We found that the introduction of such a machine requires one to have a large capacity,—that is, more than 100 ha per machine—in the absence of a government subsidy. If dairy farmers are willing to establish a corn-contractor sideline, they need to be invited to share in the use of this implement with others in order to attain a high capacity. In addition, the introduction of new seed varieties or cropping patterns should be considered to extend the appropriate harvesting time.