To provide an input pen whose storage space is reduced and which can be easily attached to an electronic device body.

An input pen 10 has an annular shape partially cut at a notch portion C, as a whole viewed in a direction indicated by an arrow A. At the notch portion C, a first end portion 12 and a second end portion 22 face each other. An inner region Rx and an outer region Ry of the annular shape connect with each other at the notch portion C. A first facing surface 13 and a second facing surface 23 form a tapered shape opening on the outer region Ry side. A line segment L1 on the first end portion 12 side of a straight line L perpendicular to a tangent at and passing through a contact point P1 of the first facing surface 13 in contact with a belt 32 does not pass the inner region Rx.