A slide assist device includes a draw-in unit including a case attached to one of a main body or a mobile body, a slider slidably placed on the case, a latch pivotally supported in the slider and switchable between a standby position locking in a corresponding portion of the case and a draw-in position releasing the locking; and an urging device; and an actuating member attached to the other of the main body or the mobile body, switching the latch from the standby position to the draw-in position, or from the draw-in position to the standby position. The latch includes an axis portion having a flat surface and rotatably fits in an axis hole of the slider and forming a positional control surface corresponding to the flat surface. When the latch is switched to the standby position, the flat surface and the positional control surface face each other.