PURPOSE: To prevent the clogging of an air cleaner in a vehicular heating device equipped with a turbo heater by setting the sectional area of the discharge side pipeline of a blower to the specified value so as to prevent discharge air quantity from the turbo heater from exceeding the engine intake air quantity in an operating region.

CONSTITUTION: The sectional area A, of the discharge side pipeline 28 of a blower 8 is determined in such a way as to always satisfy the relation of intake air quantity Ga ≥ discharge air quantity Gth in the operating engine rotating region of a turbo heater 4 in order to prevent the led-in air quantity, at the time of leading temperature risen air into an intake passage 2 by the turbo heater 4, from exceeding the intake air quantity at this time so as to flow reversely inside the intake passage 2. It is so determined that the operating line of the turbo heater 4 enters into an illustrated oblique line region so as to further approach the illustrated intake air quantity variable line Ga in proportion to the approach to the relation intake air quantity Ga = discharge air quantity Gth in a certain speed included in the turbo heater operating region.