An image forming apparatus, comprising: a developing device that includes: a developing container that contains toner; and a developing roller that is disposed so as to be opposed to an image carrying member, with part of an outer peripheral surface thereof exposed from an opening portion of said developing container, and supplies toner to the image carrying member; a duct that communicates with a suction port that is provided in a vicinity of the opening portion of the developing container; a first fan for generating an airflow in said duct and discharging air that has passed through the suction port and through the duct to an outside of a main body of the apparatus; and a dust collection part for capturing toner that has passed through the duct together with an airflow generated by said first fan, characterized in that the apparatus further comprises a connection portion that is provided at some point along a length of the duct, a main body of the connection portion has an upstream side opening portion and a downstream side opening portion which is formed in a direction orthogonal to an opening of the upstream side opening portion and is arranged such that the airflow and the toner that flow into the duct from the suction port pass through the connection portion in order of a first flow path and a second flow path, the first flow path leading from the upstream side opening portion to a flow portion inside the main body, the second flow path being in the direction orthogonal to the flow and leading from said flow portion to the downstream side opening portion, a reservoir portion for storing part of the toner that passes by together with an airflow is formed on a lower side of the flow portion, and the connection portion has a lid portion that is openable and closable at said reservoir portion, and the lid portion is disposed so as to be opposed to the upstream side opening portion. a developing device that includes: a developing container that contains toner; and a developing roller that is disposed so as to be opposed to an image carrying member, with part of an outer peripheral surface thereof exposed from an opening portion of said developing container, and supplies toner to the image carrying member; a developing container that contains toner; and a developing roller that is disposed so as to be opposed to an image carrying member, with part of an outer peripheral surface thereof exposed from an opening portion of said developing container, and supplies toner to the image carrying member; a duct that communicates with a suction port that is provided in a vicinity of the opening portion of the developing container; a first fan for generating an airflow in said duct and discharging air that has passed through the suction port and through the duct to an outside of a main body of the apparatus; and a dust collection part for capturing toner that has passed through the duct together with an airflow generated by said first fan, characterized in that the apparatus further comprises a connection portion that is provided at some point along a length of the duct, a main body of the connection portion has an upstream side opening portion and a downstream side opening portion which is formed in a direction orthogonal to an opening of the upstream side opening portion and is arranged such that the airflow and the toner that flow into the duct from the suction port pass through the connection portion in order of a first flow path and a second flow path, the first flow path leading from the upstream side opening portion to a flow portion inside the main body, the second flow path being in the direction orthogonal to the flow and leading from said flow portion to the downstream side opening portion, a reservoir portion for storing part of the toner that passes by together with an airflow is formed on a lower side of the flow portion, and the connection portion has a lid portion that is openable and closable at said reservoir portion, and the lid portion is disposed so as to be opposed to the upstream side opening portion.