An optical loss device including an optical fiber is disclosed which is characterized in that the optical loss device includes a loop portion formed by winding the optical fiber in a loop shape at least one turn, and two rotation centers that are located in a plane defined by the loop portion and that face each other, the two rotation centers forming a rotation axis located in the plane, and which is characterized in that a light of wavelength band is attenuated by twisting the loop portion around the rotation axis to vary a shape of the loop portion.