A developing device includes a developing chamber; a toner carrier disposed in the developing chamber; a toner supply part configured to supply toner to the toner carrier; a toner amount detecting part configured to change its rotational position according to the amount of toner near the toner supply part to detect the amount of toner remaining in the developing chamber; and a toner flow restricting part configured to block movement of the toner around the toner amount detecting part which is caused by a flow of the toner in the developing chamber generated by the rotation of the toner supply part and the toner carrier.