An image forming apparatus includes an output shaft including a columnar part and a D cut part connected to the columnar part and having a D section, and an electromagnetic clutch including a cylindrical member fitted to the output shaft. The image forming apparatus further includes a key member. The key member includes a conductive member. When the D cut part of the output shaft is employed as an insertion tip side and the output shaft has been inserted to the cylindrical member from one side in an axial direction, the key member is configured to fill a space between the sectional circular part of the inner peripheral surface of the cylindrical member and the D cut part of the output shaft.