To provide a rotational position sensor, capable of improving the detection accuracy and improving slide durability.

This rotational position sensor is equipped with an arm 3, equipped with a rocking part 3b rocking by fulcruming a prescribed position and a rotation axis part 3a which is connected vertically to the rocking part 3b and rotating around the axis, corresponding to the rotation quantity of a rotational output source, a frame 2 where the rotation axis part 3a is rotatably inserted, a holder 4 mounted on the arm 3, and a resistor 7 mounted on the holder 4, where a contact 5 is slidingly contacted. The rotational position sensor transfers the rotation quantity of the rotational output source to the contact 5 via the arm 3, and moves the contact 5 on the resistor 7, to thereby detect the rotation quantity as the change in the resistance value. At least a part of the frame 2 is arranged between the rocking part 3b and the holder and is equipped with a contact part 2f to be brought into contact with the rocking part at rocking of the arm 3.