A solid-liquid separator using a roller system includes a casing, rollers disposed within the casing and each provided with a screen that is formed in an outer periphery thereof with plural pores, a supply device disposed outside the rollers for supplying into the casing under appropriate pressure a solid-liquid mixture to be separated into a solid component via the plural pores and a liquid component filtered inside, a casing wall disposed adjacent to the rollers after the solid-liquid mixture supplied with the supply device is passed through the rollers rotated, a discharge window formed in the casing wall for discharging the solid component, and a pressure application lid formed on the casing wall for stably applying prescribed pressure in a direction of closing the discharge window with a pressure application device. The liquid component is separated from the solid-liquid mixture by means of the rollers and the solid component is discharged from the discharge window on which pressure has been exerted by means of the pressure application lid.