To provide a technology capable of imparting an allowance to a space such as the rear of a seat with a slide device.

This seat with the slide device includes a seat 11, a vehicle body side slide rail 21 fixed to a floor plate 4, a seat side slide rail 22 fixed to an under surface of the seat 11 and slidably fitted in the longitudinal direction to the vehicle body side slide rail 21, and a stand member 3 installed in an end part of the seat side slide rail 22 or an end part of the under surface of the seat 11 and formed so as to be freely collapsible.