To provide a die for manufacturing a silicone insulating tube, capable of preventing generation of a void.

In a molding die for manufacturing a silicone-molded silicone insulating tube having shed parts around a tube mounted with flanges 11 on its both ends, a groove 2 extending from a silicone injecting part 3 toward the both-end flanges 11 is provided in a space 2 in the die 1 to be filled with silicone. Silicone is preferentially injected from both sides of the silicone infecting part 3 of the die 1, silicone does not overhang at a shed part, and therefore generation of a void can be prevented. By causing the passage cross- section area of the groove 2 to be larger than the cross section area of one shed part obtained when the silicone insulating tube is cut by a plane including its axis, the flow of silicone at the shed parts is made smooth, and the overhang can be effectively prevented.