An optical writing device comprising: a light source (21a, 21b, 21c, 21d); an optical deflector including a mirror portion that has a plurality of deflecting surfaces and rotatable to deflect and scan light from the light source (21a, 21b, 21c, 21d); a pre-optical deflector optical system (300a, 300b) to guide the light from the light source (21a, 21b, 21c, 21d) to the optical deflector; a post-optical deflector optical system (200a, 200b) to guide the light scanned by the optical deflector to a scan target surface (6a, 6b, 6c, 6d); a cover to cover the optical deflector and surroundings of the optical deflector, the cover including at least one first opening and at least one second opening provided at different positions; and a housing to house optical elements including the light source (21 a, 21 b, 21 c, 21d), the optical deflector, the pre-optical deflector optical system (300a, 300b), the post-optical deflector optical system (200a, 200b), and the cover, wherein the light traveling from the light source (21a, 21 b, 21 c, 21d) to the optical deflector and the light deflected and scanned by the optical deflector are transmitted through the at least one first opening but not through the at least one second opening, wherein, during the rotation of the optical deflector, a forced inflow of air flowing from outside to inside the cover is generated in the at least one first opening, and a discharged airflow flowing from inside to outside the cover is generated in the at least one second opening, and wherein the optical deflector further includes a motor rotor and a rotary shaft having the mirror portion and the motor rotor fixed thereto, with the mirror portion disposed above the motor rotor in an axial direction of the rotary shaft characterized in that a maximum radius of the motor rotor is greater than a circumradius of the mirror portion, and the at least one first opening is disposed at a position facing the mirror portion in a direction perpendicular to the rotary shaft, and the at least one second opening is disposed at a position facing the motor rotor in the direction perpendicular to the rotary shaft. a light source (21a, 21b, 21c, 21d); an optical deflector including a mirror portion that has a plurality of deflecting surfaces and rotatable to deflect and scan light from the light source (21a, 21b, 21c, 21d); a pre-optical deflector optical system (300a, 300b) to guide the light from the light source (21a, 21b, 21c, 21d) to the optical deflector; a post-optical deflector optical system (200a, 200b) to guide the light scanned by the optical deflector to a scan target surface (6a, 6b, 6c, 6d); a cover to cover the optical deflector and surroundings of the optical deflector, the cover including at least one first opening and at least one second opening provided at different positions; and a housing to house optical elements including the light source (21 a, 21 b, 21 c, 21d), the optical deflector, the pre-optical deflector optical system (300a, 300b), the post-optical deflector optical system (200a, 200b), and the cover, wherein the light traveling from the light source (21a, 21 b, 21 c, 21d) to the optical deflector and the light deflected and scanned by the optical deflector are transmitted through the at least one first opening but not through the at least one second opening, wherein, during the rotation of the optical deflector, a forced inflow of air flowing from outside to inside the cover is generated in the at least one first opening, and a discharged airflow flowing from inside to outside the cover is generated in the at least one second opening, and wherein the optical deflector further includes a motor rotor and a rotary shaft having the mirror portion and the motor rotor fixed thereto, with the mirror portion disposed above the motor rotor in an axial direction of the rotary shaft characterized in that a maximum radius of the motor rotor is greater than a circumradius of the mirror portion, and the at least one first opening is disposed at a position facing the mirror portion in a direction perpendicular to the rotary shaft, and the at least one second opening is disposed at a position facing the motor rotor in the direction perpendicular to the rotary shaft.