A developing device, comprising: a developing chamber including an opening portion; a developing sleeve located in the developing chamber and partially exposed to an outside of the developing chamber through the opening portion; a magnetic member located inside the developing sleeve, the magnetic member including a separating pole and a receiving pole, the separating pole being located on a downstream side of the opening portion based on a rotating direction of the developing sleeve to separate a developing agent from the developing sleeve, and the receiving pole being located on a downstream side of the separating pole to attach the developing agent to the developing sleeve; and a magnet located between an inner wall of the developing chamber and the magnetic member, the magnet facing a region between the separating pole and the receiving pole, and the magnet having a same magnetic polarity as the separating pole and the receiving pole, wherein the inner wall includes a first air discharge hole to discharge air inside the developing chamber, the first air discharge hole including a filter to filter the developing agent, and wherein the magnet is located: adjacent the first air discharge hole, between the filter and the magnetic member, and adjacent to an upstream-side end of the first air discharge hole based on the rotating direction of the developing sleeve, wherein the developing device further comprises a second air discharge hole located on a downstream side edge of the opening portion based on the rotating direction of the developing sleeve and located outside an effective image region in a longitudinal direction of the developing sleeve, and an air discharge path connecting the first air discharge hole to the second air discharge hole. a developing chamber including an opening portion; a developing sleeve located in the developing chamber and partially exposed to an outside of the developing chamber through the opening portion; a magnetic member located inside the developing sleeve, the magnetic member including a separating pole and a receiving pole, the separating pole being located on a downstream side of the opening portion based on a rotating direction of the developing sleeve to separate a developing agent from the developing sleeve, and the receiving pole being located on a downstream side of the separating pole to attach the developing agent to the developing sleeve; and a magnet located between an inner wall of the developing chamber and the magnetic member, the magnet facing a region between the separating pole and the receiving pole, and the magnet having a same magnetic polarity as the separating pole and the receiving pole, wherein the inner wall includes a first air discharge hole to discharge air inside the developing chamber, the first air discharge hole including a filter to filter the developing agent, and wherein the magnet is located: adjacent the first air discharge hole, between the filter and the magnetic member, and adjacent to an upstream-side end of the first air discharge hole based on the rotating direction of the developing sleeve, wherein the developing device further comprises a second air discharge hole located on a downstream side edge of the opening portion based on the rotating direction of the developing sleeve and located outside an effective image region in a longitudinal direction of the developing sleeve, and an air discharge path connecting the first air discharge hole to the second air discharge hole.