A rotatable operating member which reduces manufacturing costs and prevents false detection of a rotation angle has a member and a sheet. The member has a circumferential surface, and the sheet is fixed to the circumferential surface of the member. A reflectivity of a surface of the sheet is different from a reflectivity of the circumferential surface of the member. The sheet has a plurality of holes with width A formed side by side in a circumferential direction and the sheet is fixed such that a gap with width A is provided between both ends of the sheet in the circumferential direction. A part of the circumferential surface is regularly exposed from the holes and the gap in a circumferential direction of the member.