The invention relates to a diffusion device (72) for diffusing a volatile substance, comprising: – a housing (12) internally comprising an air circulation circuit extending between an air inlet and at least one air outlet, – a ventilation means arranged in the air circuit and able to cause a flow of air to circulate from the inlet to the air outlet, and – a receiving zone (70) arranged in the air circuit downstream of the ventilation means and intended to accept a substrate (68) holding a volatile, preferably odorant, substance. According to the invention, the device comprises: a movement path (74) for the substrate (68) formed inside the housing (12) and extending between a first opening (76) and s second opening (78) which openings are formed in walls (18, 22) of the housing and intercept the air circuit at the level of the receiving zone (70).
