A ventilation fan unit with a heater, including: a frame with an opening provided at the underside of the frame; a cover having an air outlet and an air inlet provided at the opening of the frame; a snail-shaped casing with an air exit provided in the frame; a circulating fan enclosed in the snail-shaped casing; and a heating portion including a spiral heater mounted at the air exit of the snail-shaped casing, wherein the heating portion is communicated with the circulating fan through the air exit, wherein an axis of a spiral shape of the heater is in parallel with a rotation axis of the circulating fan, wherein the rotation axis of the circulating fan is located obliquely above the axis of the spiral shape of the heater.