PURPOSE: To fix a furnace easily and reliably without interference with other parts, by fitting the furnace in a recess formed in the rear face of an instrument panel while covering the furnace position exposed from the opening of the recess with the wall face of an air-conditioner duct.

CONSTITUTION: A pair of projected walls 20, 21 facing along the arranging path of a furnace 7 for electric parts are formed integrally on the rear face 8 of an instrument panel 1 in a car along the width direction, and a recess 22 for fitting the furnace 7 is formed between them. After holding the furnace 7 in the recess 22, an air-conditioning duct 15 is fixed to a boss 23 projected from the rear face 8 of said panel 1 through a screw 24 and to cover the portion of furnace 7 exposed from the opening 26 of the recess 22 with the wall face 25 of said duct 15. Consequently the furnace 7 can be fixed easily and reliably to prevent the noise due to the flexure of furnace 7 or the interference of the furnace 7 with other parts.