Disclosed is an optical deflector which includes: a polygonal mirror, a drive motor, a cover member, and a temperature detection unit. The cover member includes: a first cover portion defining a first space in which the polygonal mirror is installed, wherein the first cover portion is formed with a first opening opened in opposed relation to an outer peripheral surface of the polygonal mirror; a second cover portion defining a second space which is communicated with the first space and in which the drive motor is installed, wherein the second cover portion is formed with a second opening opened in opposed relation to a motor body of the drive motor; and a third cover portion defining a third space which is communicated with the second space. The temperature detection unit is mounted to the third cover portion so as to close the third space.