To provide a jig for pipe cutting capable of facilitating perpendicular cutting to the longitudinal direction.

This cutting jig for a down spout has a clamping part 1 furnished with a pair of frame bodies 1a, 1b to face against each other with an inner peripheral surface showing a semi circular arc shape and forming a circular space to clamp a pipe P on the inner peripheral surface as each of one end parts of each of these frame bodies 1a, 1b is axially installed on each other and a collar type cutting guide part 2 constituted of extended parts 3a, 3b to be engaged with other end parts of an opposite provided on each of the other end parts of the frame bodies 1a, 1b and a pair of projected pieces 2a, 2b projected and provided roughly at right angles in the outer peripheral direction from side edges of an inner peripheral surface of each of the frame bodies 1a, 1b.