A developing method in a developer device having a developing roller configured to rotate within a housing, the developing roller having a first portion that is exposed through an opening of the housing, a second portion at which developer attached to the developing roller separates from the developing roller and a third portion between the first and second portions, and an elastic sheet in contact with the developing roller between the second and third portions of the developing roller, the method includes guiding airflow along a first airflow passage, which is formed in the housing and partially facing the second portion of the developing roller, and guiding airflow along a second airflow passage facing the third portion of the developing roller and adjacent to the first airflow passage.