To provide a method of forming an optimum simple-structure passage for cooling medium given that the passage for the cooling medium is to pass through the portion where alleviated cooling is desired, when such forming of the passage for the cooling medium is intended for the portion where intensified cooling is desired.

In the vertical casting mold for the aluminum wheel, when forming a passage for cooling medium in the lower metal mold comprising a wheel fitting portion and a molten metal pouring inlet, first a continuous, circular state deep channel is formed on the surface of the opposite side of the cavity of the lower metal mold. Then holes are drilled at plural positions circumferentially divided toward the wheel fitting portion from the foregoing deep channel, heat insulation pipes are fit and fixed on the inner surface of the foregoing cylindrical forms (except the end part thereof), a partition plate is deposited within the foregoing heat insulation pipe so that the flow of the cooling medium through one half-round shaped partitioned part therein will be bent once at the end, and will return through the other partitioned part. Finally, the whole part of the deep channel is covered with a lid (with the exception of the inlet and outlet portions), thus forming a passage for cooling medium.