To provide an automatic solid-liquid separation device completing solid-liquid separation before disposal of excrement and a simple toilet using it.

The device includes a device body 11 formed with a through hole 11 vertically penetrating it, and a constriction 12 is formed at the vertical center of the device body 10. The portion of the body under the constriction 12 increases in diameter for a broadening shape. Solid excrement S is made to fall vertically after passing through the constriction 12, while liquid excrement L is made to flow down the inner wall of the broadening shape and outside the area where the solid excrement drops.