PURPOSE: To maintain the room temperature so as to be constant at a set value by controlling the number of revolutions of a blower for convection for oil, gas heaters or the like.

CONSTITUTION: This apparatus is provided with an adjusting means 28 which is used in the determining of an adjusting value for adjusting the number of revolutions of a blower 4, a memory means 43 in which a control level is stored to control the number of revolutions of the blower 4 and a calculation means 44 which calculates a correction value for distributing the adjusting value evenly according to the control level. An arithmetic means 45 is incorporated to compute a objective control value in the controlling of the number of revolutions of the blower 4 by adding the correction value calculated by the calculation means 44 to the control level while a control circuit section 29 is provided to perform a function of applying a voltage being applied to the blower rotating at an arbitrary part of the control level shifting the phase thereof by a value equivalent to the objective control value.