A vehicular seat slide device is provided with a lower an upper rail, a lock member, a memory piece, a memory link, a slide member, and a stopper member. The memory piece is engaged with the upper rail and the lower rail. The memory link releases the lock member and the memory piece with urging force of a memory link urging member, and pivots in a releasing direction to press the lock member in a pivot direction and press the memory piece against the urging force of the memory piece urging member. The slide member releases the memory link with urging force of a slider urging member, and presses the memory link in the release direction by moving as a seat back is collapsed forward. After the seatback is collapsed forward and the upper rail is moved in a seat-rearward direction, the stopper member contacts the memory piece.