Rotational operation device

A rotational operation device comprising:

• a rotation shaft rotated when an operation member is rotated;
• a holder fixed to the rotation shaft;
• a torsion coil spring including a coil and two protrusions located at opposite ends of the coil, wherein the rotation shaft is inserted through the coil;
• and
• a case that accommodates the holder and the torsion coil spring, wherein
• the holder and the case are configured to twist the coil when the rotation shaft is rotated by restricting movement of one of the protrusions with the case and pushing the other one of the protrusions in a rotation direction of the rotation shaft with the holder,
• the case includes a first groove that receives the one of the protrusions,
• the holder includes a second groove that receives the other one of the protrusions,
• the two protrusions are spaced apart in an axial direction of the rotation shaft by an interval that is invariable and set by a fixed length between the first groove of the case and the second groove of the holder, and
• the fixed length is set to a distance that produces a gap between windings of the coil when the torsion coil spring is in a load-free state, with the two protrusions supported by the first and second grooves.