To provide a widening device of an elastic stretchable sheet, having no risk of damaging a needle, in the case where a power supply of a motor is turned off carelessly.

A widening device 3 of an elastic stretchable sheet S1 for extending the elastic stretchable sheet S1, which is stretchable in a width direction X perpendicular to a conveying direction, in the width direction X. The widening device includes: a pair of rotors 30 facing each other and in which a delivery position R2 for delivering the sheet S1 in a downstream position is more spaced each other in comparison with a receiving position R1 for receiving the sheet S1 in an upstream position; a plurality of needles N disposed in an outer circumference of the rotor 30 and stuck in the sheet S1 to hold the sheet S1; and first switching means 6 for switching a projecting position P1 where a plurality of needles N is projected from the outer circumference of the rotor 30 and can stick in the sheet S1 and a retracted position P2 where the plurality of needles N is drawn from the outer circumference of the rotor 30 and cannot stick in the sheet S1, regardless of the phase of the rotor 30.