To slide down and contract a tent sheet 1 in a single operation.

This tent expanding-contracting device has the tent sheet 1 for installing a flexible round bar 1t on both side edges, a rail 2 arranged in the eaves edge direction from the ridge of a tent, and having a groove for slidingly embracing and supporting the flexible round bar 1t of the tent sheet 1, a roller 3 arranged on a pole plate of the tent so as to support the tent sheet 1, a pulling-down means 4 rotatably installed on an eaves column 8 so as to apply force in a tendency of pulling down the tent sheet 1 when pulling up the tent sheet 1 by installing a lower end part becoming an eaves edge part of the tent sheet 1, and a pulling-up device 7 connected to an upper end part of the tent sheet 1, and having a pulling-up force releasing means 76 arranged so as to pull up the tent sheet 1.