A casting mold is provided with a cavity portion and an overflow portion, and the overflow portion is connected to a gas flow path (suction path). A valve (an on-off valve, a shut-off valve) is provided between the gas flow path and the overflow portion. A heating method for a casting mold includes a step of setting the pressure in the cavity portion to a second pressure by sucking gas in the overflow portion and in the cavity portion while the valve is kept open for a second time period shorter than a first time period during casting. The heating method further includes a step of heating the casting mold by supplying molten metal into the cavity portion set at the second pressure, and solidifying the molten metal.